Initially working in Ireland, and occasionally teaming with her brother using the ring name Rebecca Knox, she soon began wrestling across Europe and North America on the independent circuit for various promotions.

In 2018, Lynch transitioned to a more aggressive character starting at SummerSlam, when she attacked Charlotte Flair, presenting herself as an unfairly treated underdog and dubbing herself "The Man", resulting in a large increase in her popularity.

She lost the SmackDown title the following month but then set the record for the longest reign as Raw Women's Champion at 399 days until going on a hiatus due to pregnancy in May 2020.

[12] Prior to beginning to train as a wrestler, she stated that she had been 'going down a bad path' involving alcohol, but wrestling helped her give it up.

Following her arrival at an ECCW show in Surrey, British Columbia, Knox feuded with Miss Chevius and defeated her, but lost to her in Port Coquitlam a month later.

[15][19] In late 2005, Knox participated in All Pro Wrestling (APW)'s third ChickFight tournament in Hayward, California; she defeated Morgan in the first round, but was eliminated by eventual winner Mariko Yoshida.

[22][23] In June 2006, Knox defeated Sweet Saraya to win the vacated World Queens of Chaos Championship at an event in Chouilly, France.

[25] In September 2006, while wrestling in Germany, Knox sustained a legit head injury, following which she claimed to have been "suffering from extremely painful headaches, loud buzzing in her left ear and vision as a result," and was also diagnosed with possible damage to her eighth cranial nerve.

[32] The next week, Lynch teamed up with Bayley in a losing effort to the BFFs: Beautiful Fierce Females (NXT Women's Champion Charlotte and Sasha Banks) in a tag-team match.

[42][43] Lynch made her official main roster debut on 13 July episode of Raw, as a fan favourite, along with Charlotte and Sasha Banks, after Stephanie McMahon called for a "revolution" in the WWE Divas division.

[45] Lynch made her in-ring debut on 20 July episode of Raw, teaming with Paige in a losing effort against Sasha Banks and Naomi.

[55] On 2 November episode of Raw, Lynch was pinned by Paige in a fatal four-way to earn a title match for Charlotte's Divas Championship.

On 30 November episode of Raw, Charlotte started displaying villainous traits after she feigned a leg injury to defeat Lynch, followed by a distraction provided by her father.

[59] Throughout December, the two's friendship continued to strain[60][61][62][63][64] and after Lynch defeated her on 4 January 2016 episode of Raw, Charlotte attacked her and solidified her heel turn.

[65] Lynch faced Charlotte for the Divas Championship three days later on SmackDown[66] and at the Royal Rumble pay-per-view event, but lost both matches after interference from Ric Flair.

[94] She received her championship rematch on 17 January 2017 episode of SmackDown, in a steel cage match but lost after interference from another La Luchadora (later revealed as the returning Mickie James).

[104][105] In October, Lynch won a fatal five-way match against Flair, Naomi, Tamina and Carmella to become the Team SmackDown's captain for Survivor Series.

[117] Following the 2018 Money in the Bank event, Lynch began a winning streak, defeating different competitors such as Billie Kay,[118] Sonya Deville,[119] Peyton Royce,[120] Mandy Rose,[121] and SmackDown Women's Champion Carmella in a non-title match.

The commentary and production team commented that Rousey's shoulders were not down for the three-count and many fans and media were left wondering if this was a legitimate botched finish.

[162] Nonetheless, with the win, Lynch gave Rousey her first WWE singles and pinfall loss and became a double champion and the only woman to hold both titles simultaneously.

The two feuds between the two pairs came to an end at the Extreme Rules event in July, after Lynch and Rollins retained both of their titles in a winners take all mixed tag team match.

[208] On 21 August 2021, following a 15-month hiatus, Lynch made her return at SummerSlam with a heel character, defeating Bianca Belair in less than half a minute to win the SmackDown Women's Championship for the fourth time.

[228] On 1 August, WWE issued a statement regarding Lynch suffering a separated shoulder in her match at SummerSlam, where she was expected to be out of action for several months.

[229] On 25 November episode of SmackDown, Lynch made her return as "The Man", being revealed as the fifth and final member of Bianca Belair's team for Survivor Series: WarGames.

[238] The match not being included on the card for SummerSlam (an event between Night of Champions and Payback) received backlash from fans on social media, with reports suggesting that both Stratus and Lynch had real-life frustrations with the decision.

[243] On the 17 November episode of SmackDown, Lynch was announced as the fourth and final member of Bianca Belair's team at Survivor Series WarGames.

[250] At King and Queen of the Ring on 25 May, Lynch lost the title to Morgan after accidental interference from Dominik Mysterio, ending her reign at 33 days.

Her entrance music is played after every goal scored on home ice by the American Hockey League's San Jose Barracuda.

[292] In September 2019, Ric Flair threatened legal action against WWE and filed a trademark for the term "The Man", which was being used as a nickname by Lynch.

[citation needed] Ric Flair began feuding with Lynch in 2021, accusing her of using the term without his explicit permission, but their dispute was resolved when he apologized to her in January 2023.