Lesnar wrestled several dark matches in 2001 and 2002 before being called up to the WWF's main roster.
Lesnar debuted on WWF television on the March 18, 2002, episode of Raw as a heel, attacking Al Snow, Maven and Spike Dudley during their match, while also being accompanied by Paul Heyman, who was seen giving instructions to Lesnar. When the brand extension was introduced in the WWF, Lesnar was drafted to the Raw brand. Later, Heyman was confirmed to be Lesnar's agent and gave Lesnar the nickname "The Next Big Thing". Lesnar's first feud was with The Hardy Boyz and Lesnar defeated Jeff Hardy by knockout after Hardy was unable to respond to referee Theodore Long at Backlash on April 21, his first official televised match. The next night on Raw, Lesnar faced off against Jeff's brother, Matt Hardy, and defeated him in the same fashion. Lesnar and Shawn Stasiak lost to The Hardy Boyz at Insurrextion on May 4 after Stasiak was pinned, but he attacked all the participants after the match. At Judgment Day on May 19, Lesnar and Heyman defeated The Hardy Boyz.
In June 2002, Lesnar won the King of the Ring tournament, defeating Bubba Ray Dudley in the first round, Booker T in the quarter-finals, Test in the semi-finals and Rob Van Dam in the finals, earning him a shot at the WWE Undisputed Championship at SummerSlam. At Vengeance on July 21, Lesnar lost to Van Dam in a WWE Intercontinental Championship match by disqualification. On July 22, Lesnar joined the SmackDown! brand. After a quick feud with Hollywood Hulk Hogan in August 2002, Lesnar defeated The Rock at SummerSlam on August 25 to become the new WWE Undisputed Champion and youngest WWE Champion at age 25. He also became the second fastest professional wrestler to win the WWE Championship since his debut (126 days) behind only Ric Flair (113 days). At the time, the WWE Undisputed Championship was being defended on both brands, so Raw General Manager Eric Bischoff expected Lesnar to return on Raw the following night. However, SmackDown! General Manager Stephanie McMahon announced that Lesnar was only required to defend the title on SmackDown! shows and events, forcing Bischoff to establish a new championship for the Raw brand (the World Heavyweight Championship), while the WWE Undisputed Championship was then renamed the WWE Championship.
Lesnar's rapid rise to the top of WWE in 2002 led to a feud with The Undertaker, which involved a match at Unforgiven on September 22. The match ended in a double disqualification, with Lesnar retained the title. Lesnar faced The Undertaker again at No Mercy, this time in a Hell in a Cell match. Leading up to the match, in the storyline, Lesnar broke The Undertaker's hand with a propane tank. Despite Heyman begging McMahon not to let The Undertaker use his cast as a weapon, the request was denied and the match went on as planned. At No Mercy, Lesnar defeated The Undertaker to retain the title, thus ending their feud. Lesnar would go on to successfully retain the WWE Championship in a handicap match with Heyman against Edge at Rebellion on October 26.
Lesnar's next opponent was Big Show, and Heyman was convinced more than anyone that Lesnar could not win, trying to talk him out of defending the title. Lesnar refused and defended the championship against Show at Survivor Series on November 17. At the pay-per view, Heyman turned on Lesnar, allowing Show to chokeslam him onto a steel chair and pin him to win the title, resulting in Lesnar's first pinfall loss in WWE. This led to Lesnar turning face for the first time. Following Survivor Series, Heyman made it clear that Lesnar would not get a rematch, and had snuck a special clause saying so into his contract. In order to gain his revenge on Big Show and Heyman, Lesnar interfered in his first title defense, which came against Kurt Angle the next month at Armageddon on December 15, where Lesnar executed the F-5 on Big Show, which enabled Angle to win the WWE Championship. On the following episode of SmackDown!, however, Angle introduced Heyman as his manager and, despite promising Lesnar a title shot earlier in the evening, declared that Lesnar still would not get it. Lesnar's rivalry with Heyman and Big Show resumed, which culminated in a match at the Royal Rumble in January 2003, with the winner being placed into the Royal Rumble later in the evening. On January 19, Lesnar would defeat Show and entered the Royal Rumble match as the #29 entry. He eliminated Matt Hardy and Team Angle (Charlie Haas and Shelton Benjamin), who at the time, were mentored by Angle as a 3-man stable. Lesnar would then eliminate The Undertaker last and win the Royal Rumble, which guaranteed him a WWE Championship match at WrestleMania XIX, since he was a SmackDown! superstar. After the Royal Rumble, Lesnar and Chris Benoit defeated Angle, Haas and Benjamin in a three-on-two handicap match at No Way Out on February 23, despite Team Angle injuring their partner, Edge, backstage before the match. At WrestleMania XIX on March 30, Lesnar defeated Angle to win his second WWE Championship; during the match, he botched a shooting star press and landed on his head and neck, resulting in a concussion. This forced Angle and Lesnar to improvise the finish of the match.
After WrestleMania XIX, Lesnar turned his attention to John Cena, who had returned from injury in February 2003 after an F-5 into a ringpost from Lesnar, with Cena claiming that Lesnar nearly ended his career and even named his new finishing move the "F.U." as a jab at the new champion. The feud ended in a match at Backlash on April 27, where Lesnar defeated Cena to retain the title. On the following episode of SmackDown!, Lesnar returned to his rivalry with Big Show after, in the storyline, he injured Rey Mysterio badly during their match at Backlash. Show's attack resulted in Mysterio being carried out on a stretcher and back board, and Show took Mysterio off the stretcher and swung the back board into the ringpost, compounding the injury. Lesnar called out Show, who demanded that Lesnar put his title on the line against him. This led to a stretcher match for the championship at Judgment Day on May 18, where Lesnar successfully retained. During the scripted rivalry on the June 12 episode of SmackDown!, Lesnar lifted Big Show off the top-rope in a superplex which caused the ring to collapse on impact. As Lesnar and Big Show continued their rivalry, Kurt Angle returned from his neck surgery and began to form a more friendly rivalry with Lesnar, as the two were allies, yet contenders for the title. At the first-ever SmackDown! brand-exclusive pay-per-view in July, Vengeance, Lesnar lost the WWE Championship to Angle in a triple threat match involving Big Show, after he was pinned by Angle.
Lesnar continued to aggressively pursue the WWE Championship despite his friendship with Angle. Mr. McMahon became involved in the angle, at first berating Lesnar, who had involved himself in McMahon's rivalry with Zach Gowen, for losing to Angle. This all turned out to be a swerve that came into focus on the August 7 episode of SmackDown! in Kelowna, British Columbia. That night, Lesnar and McMahon were to face each other in a steel cage match with Angle as the special guest referee as per McMahon's orders on the previous week's program. During the match, Lesnar had passed out due to a staged backstage incident and McMahon was set to pin him, but Angle refused to allow McMahon to win that way. As the two men began to argue, Lesnar attacked Angle with an F-5 and kept attacking Angle while McMahon watched and celebrated with him afterwards, turning heel in the process. At SummerSlam on August 24, Lesnar lost to Angle after submitting to the ankle lock. After that, Lesnar would cement his villainous turn by brutalizing smaller wrestlers and attacking his rivals on a more consistent basis. He returned to performing the F-5 into the ringpost, as he did to Spanky and Gowen, and interfered in Angle's matches on two separate occasions. On the September 18 episode of SmackDown!, Lesnar defeated Angle in an Iron Man match to win his third WWE Championship by a final score of five to four, thus ending their long-standing feud.
Lesnar successfully defended his newly won title against the debuting Paul London on October 9 episode of SmackDown!. He returned to feud with The Undertaker, as Lesnar had previously cost Undertaker the title in a match against then champion Kurt Angle, which granted him a shot at Lesnar's title. At No Mercy on October 19, Lesnar defeated Undertaker in a Biker Chain match after interference from The Full Blooded Italians and Vince McMahon. After Paul Heyman returned to WWE as SmackDown! General Manager, Lesnar aligned himself with his former manager. With Survivor Series coming up, Lesnar decided to challenge Angle to a traditional Survivor Series elimination tag team match. Lesnar chose Big Show as his first teammate, with Heyman adding a returning Nathan Jones and a debuting Matt Morgan to bring the team number to four. Angle chose Chris Benoit and The APA to join his team. However, Faarooq was injured during a match with Lesnar and Angle's team was forced to find a replacement for him. Lesnar's team picked A-Train to fill the fifth and final spot for them after he attacked John Cena, who refused to accept an invitation to join Lesnar's team. Cena instead joined Angle's team and Angle added Hardcore Holly as the fifth member (Lesnar had legitimately injured Holly the year before and he had not wrestled since). On November 16 at Survivor Series, Lesnar was eliminated after Benoit forced him to tap out to the Crippler Crossface; Lesnar's team would go on to lose the match. On the December 4 episode of SmackDown!, Lesnar successfully defended the WWE Championship against Benoit after Benoit passed out to Lesnar's debuting submission hold, the Brock Lock.
The Survivor Series in November 2003 also marked the first time Lesnar met Goldberg from the Raw brand. After Lesnar claimed in a backstage interview that he could beat anybody in the world, Goldberg interrupted the interview and introduced himself to Lesnar, shaking hands with him before leaving with a staredown. Lesnar followed this rivalry with a feud involving Hardcore Holly. In the storyline, Holly wanted revenge on Lesnar for legitimately injuring his neck during a previous match between the two in 2002 which left Holly in need of neck surgery and out of action for a year. At the Royal Rumble on January 25, 2004, Lesnar defeated Holly to retain the WWE Championship. Later in the Royal Rumble match, Lesnar attacked Goldberg with an F-5, enabling Kurt Angle to eliminate him.
Lesnar defended the WWE Championship against Eddie Guerrero at No Way Out on February 15. Goldberg attacked Lesnar with a spear while the referee was unconscious, allowing Guerrero to get a near-fall on Lesnar. Lesnar then attempted an F-5 on Guerrero but Guerrero reversed it into a DDT on the title belt and executed a frog splash to win the WWE Championship. An angry Lesnar then began feuding with Goldberg, blaming him for losing his title, and a match was set up between the two at WrestleMania XX on March 14. During the feud with Goldberg, Lesnar was also at odds with Stone Cold Steve Austin, who was shown suggesting to Goldberg that he attack Lesnar at No Way Out. After Lesnar attacked Austin on Raw and stole his four-wheeler, Austin was inserted as the special guest referee for the WrestleMania match. On the March 4 episode of SmackDown!, Lesnar defeated Hardcore Holly in his last match on a weekly WWE televised show. Behind the scenes, it was widely known that the match was Goldberg's last in WWE. Only a week before WrestleMania, rumors surfaced that Lesnar too was leaving. As a result, Lesnar's match with Goldberg became a fiasco as the fans at Madison Square Garden jeered and heckled both professional wrestlers vociferously. Goldberg won after a Jackhammer and both men subsequently received Stone Cold Stunners from Austin.
Lesnar returned to WWE on April 2, 2012, on Raw, as a heel, by confronting and delivering an F-5 to John Cena. The following week on Raw, General Manager John Laurinaitis revealed that he signed Lesnar to bring "legitimacy" back to WWE and become the "new face of the WWE". Laurinaitis also announced that Lesnar would face Cena at Extreme Rules with the Extreme Rules stipulation later added to the match. At Extreme Rules on April 29, Lesnar lost to Cena despite dominating the match.
The following night on Raw, WWE's Chief Operating Officer Triple H refused to give in to Lesnar's unreasonable contract demands (which included being given his own personal jet and having Raw renamed to Monday Night Raw Starring Brock Lesnar), resulting in Lesnar attacking him and breaking his arm with a kimura lock in storyline. The next week on Raw, Paul Heyman made his return as Lesnar's legal representative and claimed that Lesnar was quitting WWE. He later announced a lawsuit against WWE for breach of contract. At No Way Out in June, Triple H challenged Lesnar (who was not present) to a match at SummerSlam, which Lesnar refused. Stephanie McMahon would later goad Heyman into accepting the match on Lesnar's behalf on July 23 at Raw 1000. At SummerSlam on August 19, Lesnar defeated Triple H by submission after once again breaking his arm in storyline. The following night on Raw, Lesnar declared himself the new "King of Kings" and said that he would depart from WWE after his victory over Triple H, stating that he had conquered everything in the company.
Lesnar returned on the January 28, 2013, episode of Raw, confronting Mr. McMahon who was about to fire Heyman, and despite Heyman's pleas, Lesnar attacked McMahon with an F-5, breaking McMahon's pelvis in storyline. The following week during The Miz's Miz TV talk show, Raw Managing Supervisor Vickie Guerrero revealed herself as the one who signed Lesnar to a new contract to impress McMahon. On the February 25 episode of Raw, Lesnar once again attempted to attack McMahon, only to get into a brawl with the returning Triple H, which resulted in Lesnar legitimately having his head split open and requiring eighteen stitches. The following week on Raw, Triple H issued a challenge to Lesnar, requesting a rematch with him at WrestleMania 29, which Lesnar accepted but only after Triple H signed a contract and Lesnar named the stipulation. After Triple H signed the contract and assaulted Heyman, the stipulation was revealed as No Holds Barred with Triple H's career on the line. At WrestleMania 29 on April 7, Lesnar lost to Triple H after a Pedigree onto the steel steps. On the April 15 episode of Raw, Lesnar attacked 3MB (Heath Slater, Drew McIntyre, and Jinder Mahal) before Heyman challenged Triple H to face Lesnar in a steel cage match at Extreme Rules, which Triple H accepted the following week. At the event on May 19, after interference from Heyman, Lesnar defeated Triple H to end their feud. Lesnar returned on the June 17 episode of Raw, attacking Heyman's fellow client CM Punk with an F-5. Despite the accusations from Punk, Heyman claimed that he was not behind Lesnar's attack on him. However, Heyman turned on Punk in July, and claimed that Punk could not beat Lesnar, which led to Lesnar making his return and attacking Punk on the July 15 episode of Raw. The following week on Raw, Punk challenged Lesnar to a match at SummerSlam on August 18, where Lesnar defeated Punk in a no disqualification match.
On the December 30 episode of Raw, Lesnar returned with Heyman to announce his intentions to challenge the winner of the upcoming WWE World Heavyweight Championship match between Randy Orton and John Cena at the Royal Rumble. Lesnar then dared any wrestler who disapproved of that notion to challenge him, which was answered by Mark Henry, and a brawl would ensue, ending with Lesnar delivering an F-5 to Henry. The following week on Raw, Henry challenged Lesnar again, only to have Lesnar dislocate his elbow with the Kimura lock in storyline, which led Big Show to come out afterwards to confront Lesnar, thus starting a feud which was settled at the Royal Rumble on January 26, 2014, where Lesnar defeated Show after attacking him with a steel chair before the match began. On the February 24 episode of Raw, Heyman stated that Lesnar had requested a match for the WWE World Heavyweight Championship at WrestleMania XXX, but received an open contract to face anyone else of his choosing instead. The Undertaker then returned and attacked Lesnar with a chokeslam through a table, setting up their match at WrestleMania XXX. On April 6, Lesnar defeated Undertaker after executing three F-5s, ending his undefeated WrestleMania streak at 21.
On the July 21 episode of Raw, Triple H announced that Lesnar would face John Cena at SummerSlam for the WWE World Heavyweight Championship. At SummerSlam on August 17, Lesnar defeated Cena to become the WWE World Heavyweight Champion and during the match he delivered sixteen suplexes (most of which were German suplexes) and two F-5s to Cena, who barely managed any offense. On the August 19 episode of Main Event, Triple H announced that Cena was invoking his championship rematch clause against Lesnar at Night of Champions on September 21, where Lesnar was disqualified due to Seth Rollins interfering, but retained his championship, which could not be lost via disqualification. Later in the year, after Rollins reunited with The Authority, he was added to Lesnar and Cena's championship match at the Royal Rumble on January 25, 2015, making it a triple threat match, which Lesnar won despite suffering a storyline broken rib during the match.
Lesnar's next challenger was Roman Reigns, who won the Royal Rumble match to earn the right to face Lesnar for the title at WrestleMania 31 on March 29. During his main event match against Reigns, Lesnar delivered multiple suplexes and was heard exclaiming, "Suplex City, bitch!" and thereafter "Suplex City" became one of his signature catchphrases and merchandise motifs. After Lesnar and Reigns traded a few false finishes, Rollins cashed in his Money in the Bank contract while the match was in progress, thus making it a triple threat; Rollins then pinned Reigns to win the title. The following night on Raw, Lesnar tried to invoke his rematch clause and subsequently attacked commentators Booker T, John "Bradshaw" Layfield and Michael Cole, as well as a cameraman after Rollins refused the rematch, which led to Stephanie McMahon suspending Lesnar indefinitely in storyline.
Lesnar returned on the June 15 episode of Raw, being chosen by The Authority as the number one contender to Rollins' WWE World Heavyweight Championship at Battleground. On July 4, Lesnar made his first non-televised wrestling appearance for WWE since his 2012 return, defeating Kofi Kingston at The Beast in the East live event in Tokyo in a quick winning effort; he also delivered F-5s to Kingston's New Day stablemates Big E and Xavier Woods after the match. At Battleground on July 19, Lesnar dominated Rollins, delivering thirteen suplexes, but mid-pinfall, after performing an F-5, he was attacked by The Undertaker (who incapacitated Lesnar with a chokeslam and two Tombstone Piledrivers), thus ending the match with Lesnar winning by disqualification and Rollins retaining the championship.
The following night on Raw, Undertaker explained that he had attacked Lesnar not for ending his WrestleMania streak, but rather for Lesnar allowing Heyman to constantly taunt Undertaker about it, which led to the two brawling throughout the arena and a WrestleMania rematch being scheduled for SummerSlam on August 18, where Undertaker would controversially defeat Lesnar; during the match, Undertaker submitted to a Kimura lock by Lesnar and the timekeeper rang the bell but the referee did not see the submission and demanded that the match continue, which saw Undertaker then attack Lesnar with a low blow and Lesnar pass out to Hell's Gate. The following night on Raw, Lesnar and Heyman challenged Undertaker to an immediate rematch, only to be confronted by Bo Dallas (who mocked Lesnar about his defeat), whom Lesnar then responded by performing three German suplexes and an F-5. During Night of Champions on September 20, it was announced that Lesnar would face The Undertaker at Hell in a Cell on October 25, where Lesnar defeated The Undertaker after a low blow and F-5 onto the exposed ring floor, ending their feud. The match was later voted "Match of the Year" during the 2015 Slammy Awards.
On the January 11, 2016, episode of Raw, Lesnar returned, attacking The New Day, The League of Nations (Sheamus, King Barrett, Rusev and Alberto Del Rio) and Kevin Owens, before performing an F-5 on Roman Reigns. The following week on Raw, Lesnar would brawl with Reigns until they were both attacked by The Wyatt Family. At the Royal Rumble on January 24, Lesnar was the 23rd entrant, eliminating four competitors before being eliminated by Bray Wyatt with help from the rest of The Wyatt Family. On the January 25 episode of Raw, Stephanie McMahon announced that the main event of Fastlane would be a triple threat match between Lesnar, Roman Reigns and Dean Ambrose to determine who would face Triple H for the WWE World Heavyweight Championship at WrestleMania 32. In the following weeks, Lesnar would be continuously provoked by Ambrose, with Reigns saving him from the subsequent attacks by Lesnar. At Fastlane on February 21, Lesnar dominated most of the match before he was put through two broadcast tables by Ambrose and Reigns; he would ultimately lose the match after Reigns pinned Ambrose. Because of this, Lesnar attacked Ambrose in the parking lot as he was arriving at the arena. Ambrose returned later in the night, having hijacked an ambulance, and challenged Lesnar to a No Holds Barred Street Fight match at WrestleMania 32 on April 3, where Lesnar defeated Ambrose after an F-5 onto a pile of chairs.
On the July 7 episode of SmackDown, it was announced that Lesnar would be facing Randy Orton at SummerSlam, who himself had just returned to WWE from injury. On July 19 at the 2016 WWE draft, Lesnar was the #5 draft pick for the Raw brand. Orton was drafted to SmackDown, thus making their match an interbrand match, while WWE billed their face-off as a match fifteen years in the making. Along with Heyman, Lesnar made his return to Raw on August 1 (his first appearance on WWE programming since WrestleMania 32), but during his segment Orton appeared and attacked Lesnar with an RKO. Lesnar then attacked Orton during his match the following night on SmackDown Live, performing an F-5 on Orton. At SummerSlam on August 21, Lesnar defeated Orton by technical knockout, leaving Orton with a forehead wound which required ten staples. Much to Shane McMahon's dismay, Lesnar would later attack Shane with an F-5. Lesnar was later storyline fined $500 for delivering an F-5 to SmackDown Commissioner Shane McMahon and his assault on Orton. On September 24 at a house show in Chicago, Illinois, Lesnar defeated Orton in a no-disqualification rematch, with the match being billed as a "Suplex City death match."
On the October 10 episode of Raw, Heyman, on Lesnar's behalf, challenged Goldberg to a fight after the pair had been feuding for several months through social media and during promotional work for the WWE 2K17 video game, which featured Lesnar as the cover star and Goldberg as the pre-order bonus. Heyman stated that Goldberg was the one blemish on Lesnar's WWE career, as Goldberg had defeated Lesnar at WrestleMania XX in 2004. On the October 17 episode of Raw, Goldberg returned to WWE after a twelve-year absence and accepted Lesnar's request for a fight with their match later scheduled for Survivor Series. On the final Raw before Survivor Series, Lesnar and Goldberg had a confrontation for the first time in twelve years, resulting in a brawl with security after Heyman insulted Goldberg's family. On November 20 at Survivor Series, Lesnar lost to Goldberg in 1 minute and 26 seconds, marking the first time in three years that Lesnar was pinned. The next night on Raw, Goldberg declared himself the first entrant in the 2017 Royal Rumble match. The following week on Raw, Heyman addressed the Survivor Series match, stating that they underestimated Goldberg and that the match was a humiliation and embarrassment for him and Lesnar, who would also be in the Royal Rumble as he has something to prove. Lesnar returned on the January 16 episode of Raw to confront other Royal Rumble participants, attacking Sami Zayn, Seth Rollins, and Roman Reigns. At the Royal Rumble on January 29, Lesnar entered at number 26 and went on to eliminate Enzo Amore, Dean Ambrose and Dolph Ziggler before confronting Goldberg, who entered at number 28 and quickly eliminated Lesnar after a spear.
The following night on Raw, Lesnar challenged Goldberg to a final match at WrestleMania 33. On the February 6 episode of Raw, Goldberg would accept Lesnar's challenge whilst also being named number one contender for Kevin Owens' Universal Championship, which he won at Fastlane, thus turning his match with Lesnar into a title match. At WrestleMania 33, Lesnar beat Goldberg to win his fifth world title in WWE and became the first man to have won both the WWE Championship and the Universal Championship. Lesnar also became the second person to kick-out from Goldberg's Jackhammer and gave him the first clean singles loss of his professional wrestling career. After several weeks of feuding, Lesnar's first title defense came at the inaugural Great Balls of Fire event on July 9, 2017, where he successfully retained against Samoa Joe, before defeating him a second time for the title at a live event.
On the July 31 episode of Raw, Raw General Manager Kurt Angle announced that Lesnar would defend his title in a fatal four-way match at SummerSlam against Joe, Roman Reigns, and Braun Strowman. Lesnar and Heyman then appeared, announcing that both would leave WWE should Lesnar lose the championship in the match. At the event, Lesnar successfully retained the title by pinning Reigns. The next night on Raw, Lesnar was attacked by Strowman; it was later announced that the two would face for the title at No Mercy, which Lesnar won. Lesnar then defeated WWE Champion AJ Styles in an interbrand Champion vs Champion non-title match at Survivor Series. His next title defense was scheduled for the Royal Rumble where he successfully defended the title in a triple threat match against Strowman and Kane. Lesnar then re-ignited his feud with Roman Reigns, who won the Elimination Chamber match at Elimination Chamber to become the number one contender to Lesnar's title at WrestleMania 34. At the event, Lesnar pinned Reigns to retain the title in the main event. On April 9, it was announced Lesnar re-signed with the WWE and he would defend the title against Reigns in a rematch at the Greatest Royal Rumble pay-per-view, this time inside a steel cage. At the event, Lesnar defeated Reigns as Reigns speared Lesnar through the cage and thus giving the accidental win to Lesnar as he escaped the cage first per the rules.
At Extreme Rules, Raw General Manager Kurt Angle threatened to strip Lesnar of the Universal Title if he did now show up to Raw the following night, since Lesnar had not appeared on television since the Greatest Royal Rumble nearly three months prior. The following night on Raw, Angle was interrupted by Paul Heyman, who agreed that Brock would defend his title at SummerSlam; Reigns became the number one contender later that same night.
Lesnar returned to WWE programming on the July 30 episode of Raw, per orders of Angle, otherwise Lesnar would be stripped of the Universal Championship. Despite being at the arena, Lesnar refused to appear in the ring, and Angle threatened to fire Heyman if Lesnar failed to do so. Throughout the broadcast, Heyman unsuccessfully attempted to convince Lesnar to appear, with Lesnar going as far as to threaten Heyman. At the end of the show, Lesnar appeared after Angle fired Heyman and called Lesnar the worst Universal champion in WWE history, and subsequently attacked Angle with the F-5 before choking Heyman. Two weeks later, Heyman revealed it was all just a ruse with Lesnar returning on the August 13 episode of Raw to attack Reigns. At SummerSlam, Strowman was at ringside ready to cash in his Money in the Bank contract on the winner. Lesnar incapacitated Strowman, allowing Reigns to capitalize on the distracted Lesnar and win the Universal Championship, ending Lesnar's title reign at 504 days, which had surpassed CM Punk's WWE Championship reign of 434 days as "the longest of the modern era". The reign became the sixth longest world championship reign in WWE history and the longest since 1988.
Lesnar returned at the Hell in a Cell pay-per-view in September, interrupting the Hell in a Cell match between defending Universal Champion Reigns and Strowman, kicking in the door and attacking both men, thus rendering the match a no-contest and costing Strowman his Money in the Bank cash-in match. The next night on Raw, Acting General Manager Baron Corbin announced that Lesnar would challenge Reigns and Strowman in a triple threat match for the Universal Championship at the Crown Jewel event on November 2. On October 22, however, the match was changed to a singles match between Lesnar and Strowman for the vacant title after Reigns was forced to relinquish it due to being diagnosed with a leukemia relapse. At the event, Lesnar defeated Strowman in three minutes to become the first two-time Universal Champion, thanks to a pre-match attack from Baron Corbin.
After his title win it was announced that he would face WWE Champion AJ Styles at Survivor Series in a Champion vs Champion non-title match. However, five days before Survivor Series, Styles lost his title to Daniel Bryan on that night's episode of SmackDown Live, meaning Lesnar would face Bryan at Survivor Series. At the event, Lesnar overcame a late rally from Bryan to defeat him in the main event. Lesnar then successfully defended the title against Finn Bálor via submission at Royal Rumble on January 27, 2019. The next night on Raw, Lesnar attacked 2019 Royal Rumble match winner Seth Rollins with six F-5's, thus setting up a title match for WrestleMania 35. At the event, Lesnar attacked Rollins before the match. After the match officially started, Rollins attacked Lesnar with a low blow while the referee was down and pinned Lesnar, ending his second reign as Universal Champion at 156 days.
At Money in the Bank on May 19, 2019, Lesnar was an unannounced replacement for Sami Zayn in the Money in the Bank ladder match. Prior to the match, Zayn had been attacked backstage. Later, the match began with only seven of the scheduled eight participants. At the climax of the match, Lesnar ran-in unannounced, took out Ali, who was on top of a ladder, and then won the Money in the Bank contract, granting him either a Universal Championship or WWE Championship match at any time of his choosing within the next 365 days. After teasing cashing in on Universal Champion Seth Rollins and WWE Champion Kofi Kingston and failing an attempt to cash-in on Rollins at Super Showdown, Lesnar successfully cashed in his contract to win the Universal Championship from Rollins at Extreme Rules on July 14 right after Rollins and Raw Women's Champion Becky Lynch had retained their respective titles against Baron Corbin and Lacey Evans in a Last Chance Winners Take All Extreme Rules mixed tag team match. This made Lesnar the first wrestler to successfully cash in on the Universal Championship, as well as becoming a record three-time Universal Champion. Rollins then earned a rematch against Lesnar at SummerSlam on August 11. At the event, Lesnar lost the title to Rollins thus ending his third title reign at 28 days.
Lesnar and Heyman returned on the September 17 episode of SmackDown and issued a challenge to Kofi Kingston for the WWE Championship on SmackDown's 20th Anniversary on October 4. Kingston accepted and Lesnar proceeded to F5 him. At the event, Lesnar quickly defeated Kingston to win his fifth WWE Championship. After his victory, Lesnar was attacked by the debuting Cain Velasquez. Lesnar was then scheduled to defend the WWE Championship against Velasquez at Crown Jewel on October 31. Also during this time, as part of the 2019 draft, Lesnar was drafted to SmackDown. At Crown Jewel, Lesnar retained against Velasquez in just two minutes. The following night, on the November 1 episode of Friday Night SmackDown, Lesnar quit the brand and returned to Raw, taking the WWE Championship with him. This led to Mysterio challenging Lesnar for the championship at Survivor Series, which was made official as a No Holds Barred match, where Lesnar retained, despite Dominic's attempt to aid Mysterio during the match.
Lesnar returned on the January 6 episode of Raw to declare that no one deserved an opportunity at his championship at the Royal Rumble, so instead he would enter the Royal Rumble match as entrant number one, aiming to become the first reigning WWE champion to win the Rumble match since Hulk Hogan in 1990. At the event on January 26, Lesnar eliminated the first thirteen competitors he faced, tying the record for most eliminations in a Rumble match, before being eliminated by Drew McIntyre, who ultimately won the match. At Super ShowDown, Brock Lesnar defeated Ricochet in under two minutes. Lesnar's fifth WWE Championship reign was ended by Drew McIntyre during WrestleMania 36 on April 5, 2020. On August 31, 2020, it was reported that Lesnar was no longer under contract with WWE.
Lesnar returned at SummerSlam on August 21, 2021 as a face confronting Universal Champion Roman Reigns after his successful title defense against John Cena, sporting a new beard and ponytail look. His confrontation with Reigns resulted in him becoming a member of the SmackDown roster. On the September 10 episode of SmackDown, he confronted Reigns, claiming Paul Heyman was aware he would appear at SummerSlam. He proceded to challenge Reigns for a match for the Universal Championship, but was attacked by Reigns and the Usos. During the October 1 episode of SmackDown, he again confronted and brawled with Reigns and the Usos. A match for the Universal Championship bewteen Lesnar and Reigns was ultimately scheduled for Crown Jewel, where Lesnar lost to Reigns after interference from the Usos. On the following episode of SmackDown, he started a locker room-clearing brawl with Reigns, resulting in an indefinite suspension by on-air authority figure Adam Pearce, who Lesnar attacked afterwards. On October 27, he was officially drafted to the SmackDown brand despite being suspended in storyline. On the November 26 episode of SmackDown, it was announced his suspension had been lifted. On the December 3 episode of SmackDown,, it was announced that Lesnar would once again face Reigns for the title, this time at the Day 1 event. However, the match was canceled due to illness, and Lesnar was instead added to Raw's WWE Championship match at the event to make it a fatal five-way match. At Day 1, Lesnar won his sixth WWE Championship, defeating Seth Rollins, Kevin Owens, Bobby Lashley, and defending champion Big E, who he pinned. On the following episode of Raw, Lesnar reunited with his advocate Paul Heyman, whilst it was confirmed he would defend his newly won championship against Lashley at Royal Rumble. At the Royal Rumble, he lost the WWE Championship to Lashley with the help of Reigns' interference, ending his sixth reign at 29 days. Later that night, he entered the Royal Rumble match as the surprise thirtieth entrant and won, last eliminating Drew McIntyre. On the following episode of Raw, Lesnar revealed he would challenge Reigns for the Universal Championship at WrestleMania 38. He was also scheduled to compete in the WWE Championship Elimination Chamber match at Elimination Chamber. In what was his first time competing in an Elimination Chamber match, Lesnar won to capture the WWE Championship for a seventh time, also converting his Universal Championship match against Reigns at WrestleMania into a "Winner Takes All" match. The following night on Raw, their Winner Takes All match was then stipulated as a title unification match. At the event, Lesnar lost the WWE Championship to Reigns in a unification match.
After a two-month hiatus, Lesnar made his return after Reigns retained the Undisputed WWE Universal Championship against Riddle on an episode of SmackDown. It looked like he wanted to let bygones be bygones, but it ended up with Lesnar hitting three F5's respectively on the Bloodline. This set up another clash between the two at SummerSlam for the Undisputed WWE Universal Championship in a Last Man Standing match. At the event on July 30, Lesnar failed to beat Reigns for the title, ending their feud.
On the October 10 episode of Raw, Lesnar made a surprise return, attacking United States Champion Bobby Lashley and injuring his shoulder before his scheduled title defense against Seth "Freakin" Rollins, resuming their feud. At Crown Jewel on November 5, Lesnar defeated Lashley. Lesnar's next appearance occurred on Raw is XXX on January 23, 2023, where he caused Bobby Lashley to lose his United States Championship match against the champion, Theory. At the Royal Rumble, Lesnar entered the Royal Rumble match at number twelve, but was eliminated by Lashley. At Elimination Chamber on February 18, Lesnar lost to Lashley by disqualification after he hit Lashley with a low blow and attacked both the referee and Lashley.
On the February 20 episode of Raw, Omos challenged Lesnar to a match at WrestleMania 39. The following week on Raw, Lesnar appeared on the VIP Lounge with Omos' manager MVP; Lesnar accepted the challenge, and then proceeded to attack MVP with an F-5. At the event, Brock won the match against Omos. On April 3 episode of Raw on the day after Night Two of WrestleMania 39, Cody Rhodes challenged Roman Reigns and Solo Sikoa to a tag team match later that night, and Reigns accepted under the condition that Rhodes' partner was someone who competed at WrestleMania 39. Lesnar answered; however, the match never occurred due to Lesnar viciously assaulting Rhodes before the match could begin, turning heel for the first time since 2020. Rhodes addressed the attack the following week and challenged Lesnar to a match at Backlash. On the April 17 episode of Raw, Rhodes appeared ready to fight despite not being medically cleared to compete. To keep Rhodes from fighting Lesnar that night, WWE official Adam Pearce made the match for Backlash official. Rhodes went on to defeat Lesnar at Backlash. Lesnar then went on to defeat Rhodes at Night of Champions by submission after Lesnar broke Rhodes arm. Rhodes then went on to defeat Lesnar at SummerSlam, ending their feud. After the match, Lesnar embraced Rhodes, thus seemingly reverting him back into a babyface.