Rousey, along with friends Shayna Baszler, Jessamyn Duke, and Marina Shafir, were acknowledged on camera and commentary, in the front row at WWE's SummerSlam event in August 2014. The group also went backstage during the event, meeting Paul Heyman, among others.
At WrestleMania 31 in March 2015, the four women were seated in the front row. During an in-ring argument between The Rock and The Authority (Stephanie McMahon and Triple H), McMahon slapped the Rock and ordered him to leave "her ring". She taunted him, saying he would not hit a woman. He left, paused and walked over to Rousey to a loud ovation. He then helped her into the ring and said that she would be happy to hit McMahon for him. After a staredown, The Rock attacked Triple H. When he stumbled toward Rousey, she tossed him out of the ring. McMahon tried to slap her, was blocked and Rousey grabbed her arm, teasing an armbar, before throwing her out of the ring. Rousey and the Rock celebrated in the ring, while the Authority retreated with the implication of revenge. The segment was replayed and discussed throughout the next night's Raw with the commentators hyping a tweet Rousey made earlier that day, in which she implied a return to WWE.
On July 13, 14, and September 12, 2017, the Rousey, Shafir, and Duke once again appeared in the audience of the Mae Young Classic to support their compatriot Shayna Baszler, who was making her WWE debut in the tournament. Additionally during the event, all four women had a face-off with Charlotte Flair, Becky Lynch, and Bayley, who, in WWE together with Sasha Banks, are also known as the Four Horsewomen, hinting at a possible future feud between the two groups.
It was reported in 2017 that Rousey had signed with the WWE on a full-time basis and had been training at the WWE Performance Center in Orlando.
Rousey made a surprise appearance at the Royal Rumble on January 28, 2018, confronting Raw Women's Champion Alexa Bliss, SmackDown Women's Champion Charlotte Flair, and Asuka, who had just won the inaugural women's Royal Rumble match. The jacket which Rousey wore during this appearance belonged to "Rowdy" Roddy Piper. On February 25 at the Elimination Chamber pay–per–view, Rousey was involved in an in–ring altercation with Triple H and Stephanie McMahon, after which she signed her contract (in storyline), thus making her a part of the Raw brand.
On the March 5 episode of Raw, it was announced that Rousey would make her in–ring debut WrestleMania 34, WWE's flagship event, in a mixed tag team match pitting Rousey and Kurt Angle as her partner against Stephanie McMahon and Triple H. At the event, Rousey submitted McMahon with her trademark armbar submission hold to secure the win for her team.
In May, after she was challenged by then–champion Nia Jax, it was announced that Rousey would get her first opportunity at the Raw Women's Championship at the next pay–per–view, Money in the Bank. At the event, Rousey went on to win the match by disqualification after an interference by Alexa Bliss, who attacked both Rousey and Jax and cashed in her Money in the Bank contract (which she won earlier that night) to win the title instead. Throughout the next two months, Rousey would start her first feud as part of WWE with Alexa Bliss over the title, which included a suspension (again in kayfabe) after Rousey attacked Bliss, Kurt Angle and multiple officials. After honoring her suspension from in–ring competition, Rousey received a Raw Women's Championship match by Raw General Manager Kurt Angle against Bliss at SummerSlam. At the event on August 19, Rousey squashed Bliss to win the title, her first championship win in WWE. In a rematch between the two that took place a month later on September 16 at Hell in a Cell, Rousey once again submitted Bliss.
Throughout her championship reign, Rousey went on to fend off title contenders such as Nikki Bella (in the main event of the first all women's pay–per–view Evolution), Mickie James, Nia Jax, Natalya, and Sasha Banks. In November, Rousey was supposed to face Becky Lynch at the Survivor Series pay–per–view in an interbrand champion vs. champion match, however, Lynch was legitimately injured during an invasion angle just minutes after she attacked Rousey backstage. At the event, Rousey faced Charlotte Flair instead, and won via disqualification after Flair attacked her with a kendo stick and steel chairs. A month later, on December 16, at TLC: Tables, Ladders & Chairs, Rousey gained revenge against both Flair and Lynch as she pushed them off a ladder during their match, also helping Asuka win the SmackDown Women's Championship. Shortly after she retained her title against Bayley, on the January 28, 2019, episode of Raw, Rousey continued her feud with Becky Lynch (who had won the Royal Rumble match) after the latter chose to challenge her in a title match at WrestleMania 35. On the February 11 episode of Raw, Vince McMahon suspended Lynch for 60 days in storyline and announced Charlotte Flair replaced Lynch as Rousey's WrestleMania opponent. On the March 4 episode of Raw, Rousey turned heel for the first time in her career when she cut a promo on fans and attacked both Flair and Lynch. At Fastlane, Lynch faced Flair in a match where if Lynch won, she would be inserted back into the Raw Women's Championship match at WrestleMania. Rousey attacked Lynch during the match, giving Lynch the disqualification victory and thus the WrestleMania triple-threat match between Rousey, Flair and Lynch was made official. On March 25, WWE announced Rousey's title defense against Lynch and Flair would be the main event of WrestleMania 35, making it the first women's match to close WrestleMania. At the event, in what was changed to a Winner takes all for Rousey's Raw and Flair's SmackDown Women's Championships, Lynch controversially pinned Rousey to win both titles. The commentary and production team commented that Rousey was in the ring saying her shoulders were not down for the full three-count and showed a replay of the ending pin-pointing this fact. Nonetheless, this gave Rousey her first loss in WWE and ended her championship reign at 232 days.
On January 29, 2022, at the Royal Rumble, Rousey returned to WWE as she entered at number twenty-eight in the women's Royal Rumble match and won by last eliminating Charlotte Flair, earning a championship match at WrestleMania 38. On the February 4 episode of SmackDown (her first SmackDown appearance), Rousey chose to challenge Flair for the SmackDown Women's Championship at WrestleMania. At Elimination Chamber, Rousey teamed with Naomi to defeat Flair and Sonya Deville. At WrestleMania 38, Rousey would lost to Flair. Rousey would however challenge Flair to a rematch on the April 8 episode of SmackDown in form of an "I Quit" match for the title at WrestleMania Backlash, which was later made official the next day. At the event, Rousey would make Flair utter the phrase and win the SmackDown Women's Championship for the first time in her career. On the May 13 edition of SmackDown, she issued an open challenge for her newly won title; Raquel Rodriguez would answer the challenge, but Rousey retained her title. In June, she would begin a feud with Natalya with both of them trading insults and taking personal jabs at each other. At Money in the Bank, Rousey defeated Natalya, but after the match, Liv Morgan successfully cashed in her Money in the Bank contract, thus ending her reign at 55 days. On July 8, it was announced that Rousey would challenge Morgan for the title at SummerSlam. On July 30, at SummerSlam, Rousey lost to Morgan in controversial fashion, with Morgan winning by pinfall despite submitting to Rousey's armbar while her shoulders were down. After the match, Rousey attacked Morgan and the referee, turning heel for the first time since 2019. As a result of attacking a referee, Rousey was suspended from WWE. In a direct violation of the suspension, Rousey crashed the SmackDown Women's Championship contract signing for Clash at the Castle, cutting a promo. After the promo, she attacked a security guard and threatened to lock in the armbar. However, she let go of the guard and walked off. After her suspension was lifted, Rousey won a fatal five-way elimination match on the September 9 episode of SmackDown to earn a rematch against Morgan for the SmackDown Women's Championship at Extreme Rules. The following week, Morgan challenged Rousey to an Extreme Rules match for the title, which Rousey accepted. At the event on October 8, Rousey defeated Morgan to win her second SmackDown Women's Championship.
On the October 28 episode of SmackDown, Rousey retained her title against the returning Emma in an open challenge. At Survivor Series WarGames on November 26, Rousey retained her title against Shotzi with help from Shayna Baszler. On the December 30 episode of SmackDown, Rousey retained her title against Raquel Rodriguez. After the match, Rousey was confronted by the returning Charlotte Flair, who challenged Rousey to an impromptu title match, which she accepted. Despite interference from Baszler, Rousey was defeated by Flair, ending her second reign at 83 days.
After a brief hiatus, Rousey returned on the February 10 episode of Raw to help Baszler attack Liv Morgan and Tegan Nox, officially beginning an alliance between the two. On Night Two of WrestleMania 39, Rousey and Baszler won the women's WrestleMania Showcase fatal four-way tag team match. As part of the 2023 WWE Draft, Rousey and Baszler were drafted to Raw. On the May 29 episode of Raw, Rousey and Baszler won a fatal four-way tag team match for the vacant WWE Women's Tag Team Championship; Rousey also became the eighth women's Triple Crown Champion with this win. On the June 23 episode of SmackDown, Rousey and Baszler defeated Alba Fyre and Isla Dawn to unify both WWE and NXT Women's Tag Team Championships. At Money in the Bank, Rousey and Baszler lost the Women's Tag Team Championships to Liv Morgan and Raquel Rodriguez, when Baszler turned on her. On the July 3 episode of Raw, Baszler confronted Rousey, frustrated as she had to pay her dues to get to the WWE, while Rousey had her first match at WrestleMania. This led into a brawl between the two, which ended with Baszler kneeing Rousey in the face. On the July 17 episode of Raw, Rousey declined Baszler's challenge to come to the ring and said she would fight her at SummerSlam, which was later stipulated as an MMA Rules match. Rousey would lose to Baszler by technical submission. Following the loss, Rousey left WWE.