Smilla Sundell

Smilla Sundell (born 12 November 2004) is a Swedish Muay Thai fighter, kickboxer, and mixed martial artist. She competed in ONE Championship, where she was the former ONE Women's Strawweight Muay Thai World Champion.

On 22 April 2022 Sundell became the youngest person to ever win a world title in Muay Thai by defeating Jackie Buntan to win the inaugural ONE Women's Strawweight Championship at 17 years and 5 months.

Since 2026, she has competed for the American MMA promotion Tuff-N-Uff, remaining undefeated through her first two professional bouts.

Early life Born in Sundbyberg, Sweden, Sundell started practicing karate at five years old for self-defense. She first tried her hand at Muay Thai at 10 or 11, while on vacation in Thailand. She and her younger sister started practicing Muay Thai at a gym called Yodyut Muay Thai due to a lack of any other sports. When Sundell was 15, her family moved back to Sweden. She has notable victories over decorated champion Sawsing Sor Sopit, Ponpan Por.Muengpetch, and male fighter Bongsak Sitpholek.

ONE Championship In her ONE Championship debut at ONE: Full Circle on 25 February 2022, Sundell faced Australia's Diandra Martin. She won the fight by TKO in round 3. This was her first fight in four-ounce MMA gloves, which are smaller than the usual gloves used in Muay Thai.

Sundell made her kickboxing debut against Milana Bjelogrlić at ONE Friday Fights 18 on 26 May 2023. She won the fight by unanimous decision.

Sundell made her first Women's Muay Thai Strawweight World title defense against ONE Women's Atomweight Muay Thai World Champion Allycia Rodrigues at ONE Fight Night 14 on 29 September 2023. She retained the championship by a third-round technical knockout. She also earned her second $50,000 Performance of the Night bonus.

In the second title defense, Sundell faced Natalia Diachkova on 4 May 2024 at ONE Fight Night 22. At the weigh-ins, Sundell came in at 126.5 lb (after coming in at 127.7 lb in for an unofficial check two and a half hours into the weigh-ins), 1.5 pounds over the strawweight limit for a title fight. As a result, Sundell was stripped of the title and only Diachkova was eligible to win it. She won the fight via technical knockout in the second round.

On 19 August 2025, it was reported that Sundell was removed from the ONE roster, her weight having exceeded its heaviest women's weight class.

Mixed martial arts career On 26 October 2025, Las Vegas-based MMA promotion Tuff-N-Uff announced that Sundell had signed with the organization. Her professional MMA debut, originally scheduled for 12 December 2025 at Tuff-N-Uff 150 against Zurina Turrey, was cancelled after Turrey was not medically cleared to compete.

Sundell made her professional MMA debut on 22 January 2026 at Tuff-N-Uff 151 in Las Vegas, defeating Miranda Barber by technical knockout (knees and elbows) at 4:54 of the first round. Following the win, UFC president Dana White publicly praised her performance on social media.

On 5 June 2026, Sundell faced American fighter Maya Stewart in a bantamweight bout at Tuff-N-Uff 154, also in Las Vegas, winning by technical knockout (referee stoppage from strikes) at 1:28 of the second round to move to 2–0 as a professional.

Championships and awards Muay Thai ONE Championship ONE Women's Strawweight Muay Thai World Championship (One time; former) Youngest person to win a world title in ONE history One successful title defense ONE Super Series Female Fighter of the Year 2022 Performance of the Night (Two times)

Mixed martial arts record Win

Maya Stewart TKO (punches and knees) Tuff-N-Uff 154

Las Vegas, Nevada, United States Win

Miranda Barber TKO (knees and elbows) Tuff-N-Uff 151

Las Vegas, Nevada, United States Muay Thai and Kickboxing record