Casey O’Neill Bio
Casey O’Neill (born 7 October 1997) is a Scottish and Australian professional mixed martial artist who competes in the women’s Flyweight division of the Ultimate Fighting Championship (UFC). Fighting out of Las Vegas, Nevada, she is trained at Fight Ready and is known for her striking style developed through years of kickboxing training. Nicknamed “King,” O’Neill turned professional in 2019 and has since built a reputation as one of the promising competitors in the 125-pound weight class.
Early Life and Background
Casey O’Neill was born in Irvine, Scotland, and spent the early years of her life in Kilmarnock. Her father, Cam O’Neill, was a professional kickboxer, and the household gave her early exposure to combat sports. She began training in kickboxing at the age of four, an unusual starting point that laid the foundation for her striking-heavy approach inside the cage.
At the age of 10, O’Neill moved with her family to Australia’s Gold Coast, where she attended Coombabah State High School. The relocation introduced her to a new training environment, and at 13 she expanded her skill set by taking up Brazilian jiu-jitsu. She currently holds a brown belt in Brazilian Jiu-Jitsu, reflecting years of consistent grappling study alongside her kickboxing base.
Path to MMA
Encouraged by her kickboxing roots, O’Neill asked her father for permission to compete in amateur MMA, and he eventually agreed. At 15 years old she fought her first amateur bout and was stopped in the first round by an opponent four years her senior. A second amateur fight the following year ended in another early first-round defeat, a stretch that pushed her to refocus her training for the next two years.
At 19, O’Neill returned to the amateur circuit and strung together five consecutive wins, proving she had closed the gap with more experienced opponents. In 2019, at 21 years old, she made the transition to the professional ranks, beginning at Strawweight before eventually settling at Flyweight. That same year she relocated to Phuket, Thailand, to sharpen her striking at the renowned Tiger Muay Thai gym, an important step in her development as a mixed martial artist.
Casey O’Neill Career
Early Career (2019–2020)
Casey O’Neill made her professional debut on 5 April 2019 at Eternal MMA 43, defeating Amira Hafizović by unanimous decision. She followed that victory with three more domestic wins against Jada Ketley, Miki Motono, and Caitlin McEwen, although her bout with Motono saw her miss weight by 0.2 kilograms and forfeit a title. The run showed her finishing ability and her ability to perform under the demands of regional MMA.
In September 2020, O’Neill took her first international fight with the UAE Warriors promotion and stopped Christina Stelliou in the second round by knockout at UAE Warriors 13. The finish drew attention from larger promotions and helped set up her next move. By the end of 2020, she had completed her stint at Tiger Muay Thai and transitioned to Xtreme Couture MMA, a change that brought her closer to the UFC talent pipeline.
UFC Breakthrough (2021–2022)
O’Neill made her UFC debut on 20 February 2021 at UFC Fight Night: Blaydes vs. Lewis, knocking out Shana Dobson in the second round. The win announced her arrival in the promotion, and four months later she submitted Lara Procópio with a third-round rear-naked choke at UFC on ESPN: The Korean Zombie vs. Ige. Each finish showed a different side of her game, from striking to grappling.
On 2 October 2021, at UFC Fight Night: Santos vs. Walker, O’Neill defeated Antonina Shevchenko by technical knockout in round two, a Performance of the Night award-winning performance. In February 2022, she outpointed veteran Roxanne Modafferi by split decision at UFC 271, a closely scored bout that 19 of 19 media outlets scored in her favor. The win was a personal milestone and further cemented her position in the flyweight division.
Fight Ready Era and Recent Years (2023–Present)
After her Modafferi win, O’Neill was scheduled to face Jessica Eye at UFC 276 in July 2022, but she withdrew in late April due to a torn ACL. The injury kept her out of competition for nearly a year, and her return to the Octagon came on 18 March 2023 at UFC 286, where she dropped a unanimous decision to Jennifer Maia. A subsequent booking against Viviane Araújo at UFC 293 was cancelled in early August 2023 because of another injury.
O’Neill returned at UFC 296 on 16 December 2023, where she was submitted by Ariane Lipski via armbar in the second round. She bounced back on 17 August 2024 at UFC 305, defeating replacement opponent Luana Santos by unanimous decision after original foe Tereza Bledá withdrew. O’Neill now trains out of Fight Ready in Las Vegas, a switch from her earlier Xtreme Couture base, and continues to develop her all-around game.
Driving Style and Strengths
O’Neill fights out of a kickboxing stance, the foundation she built under her father and at Tiger Muay Thai. Her striking remains her most polished weapon, though she has demonstrated a credible rear-naked choke and an improving grappling base from her Brazilian jiu-jitsu work. Training alongside a competitive team at Fight Ready has given her the structure to round out her game and prepare for higher-ranked opposition.
Notable Events and Milestones
Among her most memorable moments, O’Neill’s UFC debut knockout of Shana Dobson, her third-round submission of Lara Procópio, and her Performance of the Night bonus for stopping Antonina Shevchenko stand out. Her split-decision win over Roxanne Modafferi also became a talking point across the sport, as 19 of 19 media outlets scored the bout for O’Neill. Overcoming a torn ACL and multiple injury layoffs has been an equally important part of her career story.
Casey O’Neill Career Wins
Casey O’Neill’s professional record reflects 10 wins against 2 losses across 12 total bouts, with finishes spread across decisions, knockouts, and submissions. She has competed at both Strawweight and Flyweight during her career, but her current run is built at 125 pounds. Her finishing rate and her ability to bounce back from setbacks have defined her trajectory in the sport.
UFC Highlights
Inside the UFC, O’Neill’s most notable finishes are her second-round knockout of Shana Dobson, her third-round rear-naked choke of Lara Procópio, and her second-round technical knockout of Antonina Shevchenko. Her first UFC victory came in her debut in February 2021, and her most recent Octagon win came by unanimous decision over Luana Santos at UFC 305 in August 2024.
Other Wins and Performances
Outside the UFC, O’Neill captured four wins on the Australian regional circuit, including a unanimous decision over Amira Hafizović in her professional debut. She also picked up a second-round knockout of Christina Stelliou at UAE Warriors 13 in September 2020, which served as her first international victory and her introduction to a broader audience.
Casey O’Neill Family
Family Background and Fighting Lineage
O’Neill comes from a combat-sports household. Her father, Cam O’Neill, is a former professional kickboxer who introduced her to the sport at a young age and later supported her transition into MMA. The family’s relocation from Scotland to Australia’s Gold Coast helped shape her early training path and exposed her to a wider martial arts community.
Personal Life
Casey O’Neill is based in Las Vegas, Nevada, where she trains at Fight Ready. She is of Australian and British nationality, reflecting her upbringing in both Scotland and Australia, and continues to represent that dual background in her career. Public details about her marital status and children are not confirmed in available sources.
2025 Season Performance
Heading into 2025, Casey O’Neill sits ranked inside the UFC women’s flyweight top 15, listed at number 11 in the official rankings as of 9 September 2025. Her last appearance came by unanimous decision over Luana Santos at UFC 305 in August 2024, a result that steadied her momentum after a difficult stretch of injuries and losses. With a full training camp behind her, she is positioned to take on another ranked opponent in the division.
The 2025 calendar is expected to test her growth under the Fight Ready banner, where she has refined both her striking and grappling. A return to the win column at UFC 305 has given her a platform to build on, and matchmakers have continued to book her against rising contenders. Staying healthy and active will be a key theme of her year, given the ACL tear and subsequent cancellations that interrupted her previous run.
Long term, O’Neill’s outlook is tied to her ability to stack top-tier wins and climb toward title contention. Her combination of kickboxing pedigree, a brown belt in Brazilian jiu-jitsu, and a finishing instinct gives her a well-rounded profile at 125 pounds. If she remains active through 2025, she has a realistic path toward breaking into the top tier of the flyweight division.