Swedish Muay Thai sensation Smilla Sundell has officially entered mixed martial arts, signing with Tuff-N-Uff to make her professional MMA debut in December 2025. The announcement marks a significant chapter in the career of the fighter known as “The Hurricane,” who previously held the ONE Women’s Strawweight Muay Thai World Championship and stands as the youngest person to achieve a world title in Muay Thai history.
Smilla Sundell To MMA
Sundell, currently 20 years old, will compete at 135 pounds in her debut, representing a weight class selection following her departure from ONE Championship. The decision to shift weight classes shows physical growth that occurred during her tenure with the Asia-based promotion.
At weigh-ins for her May 2024 title defense against Natalia Diachkova, Sundell came in 1.5 pounds over the strawweight limit, resulting in her being stripped of her championship despite winning the bout via technical knockout in the second round. By August 2025, ONE Championship officially removed Sundell from their roster, citing her inability to compete within the organization’s available female weight classifications.
The fighter’s path to MMA prominence began through Muay Thai competition. Born in Stockholm, Sweden, on November 12, 2004, Sundell started martial arts training at age five with karate for self-defense purposes. Her introduction to Muay Thai occurred during a family vacation to Thailand when she was approximately 10 or 11 years old. What initially seemed like a temporary interest transformed into a permanent career direction when her family relocated to Koh Samui.
Training at Fairtex Gym in Pattaya from October 2019 onward, Sundell developed into an elite striker at an accelerated pace. By January 2021, at just 16 years old, she held the number one ranking among female featherweights at 57.153 kilograms according to the WBC Muay Thai. Her amateur record before joining ONE Championship included over 31 victories.
Sundell made her ONE Championship debut on February 25, 2022, at ONE: Full Circle, defeating Australia’s Diandra Martin by third-round TKO. Less than two months later, she captured the inaugural ONE Women’s Strawweight Muay Thai World Championship by defeating Jackie Buntan via unanimous decision at ONE 156 on April 22, 2022. At 17 years and 5 months old, this victory established her as the youngest world champion in ONE Championship history, a distinction that extended across all weight classes and martial arts disciplines within the organization. The performance earned her a $50,000 Performance of the Night bonus.
Sundell’s ONE Championship tenure included one successful title defense against Allycia Rodrigues on September 29, 2023, at ONE Fight Night 14, securing another technical knockout in the third round and a second $50,000 Performance of the Night award. Her competitive record within ONE encompassed five victories across Muay Thai and kickboxing disciplines without experiencing defeat before her title defense against Diachkova, though the weight management issues had become increasingly apparent.
Tuff-N-Uff, the promotion facilitating Sundell’s MMA entry, operates as the second-longest-running MMA organization in the United States, established in 1994. The promotion has developed and signed over 3,000 athletes throughout its 30-plus year history, with more than 60 fighters progressing to UFC contracts. Notable alumni include Hall-of-Famer Ronda Rousey, Women’s Bantamweight Champion Aspen Ladd, current UFC fighters Felicia Spencer and Tracy Cortez, and Khalil Rountree Jr. Tuff-N-Uff has consistently featured on UFC Fight Pass and received television coverage across multiple networks including ESPN, HBO, and specialty combat sports channels.
Sundell’s striking foundation provides a major advantage in distance management and clinch control, areas where Muay Thai training directly transfers to MMA application. At 20 years old, Sundell enters the MMA landscape significantly younger than many female fighters beginning their professional career.
The specific December 2025 date and potential opponent remain unannounced as of the announcement date, though Sundell has indicated her readiness to begin this chapter of her combat sports career.