Denise Castle (née Mellor; born 24 October 1971) is an English professional boxer and Muay Thai fighter.

In Muay Thai, she has won the mini flyweight international and world titles under the WBC Muaythai banner. In boxing, she has held the WIBA atomweight championip since 2019. Castle has been described as the "hardest mother in the world".^[1]

Mellor faced Lotta Loikkanen for the inaugural WBC Muaythai World Mini Flyweight Championship on 25 July 2010. She lost the bout by decision after five rounds.^[2][3]

Mellor faced Annie Errikson for the inaugural WBC Muaythai International Mini Flyweight Championship on 14 July 2011, at "Muaythai World Series" at O2 Academy Bournemouth in Bournemouth, England. She won the bout by unanimous decision, thus winning the title.^[4][5]

On 2 October 2011, Mellor faced Erika Kamimura for the inaugural WBC Muaythai International Light Flyweight Championship. She lost the bout via first-round knockout.^[6][7]

Mellor faced Nattaya Kantasit for the WBC Muaythai world mini flyweight title on 22 June 2012, at O2 Academy Bournemouth. She won the bout by unanimous decision to win the title.^[8]

In her boxing debut, Castle faced Dorkmaipa Keangpompetch on 9 April 2014, at the MBK Center. She won the bout via knockout.^[9]

On 2 August 2014, Castle faced Momo Koseki for WBC female atomweight title. She lost the bout by technical knockout in the eight round.^[10]

On 5 September 2018, it was revealed that Castle would face Fabiana Bytyqi for the vacant WBC atomweight title. She entered the bout following a four-year long absence from the sport. The fight took place at the Sportcentrum Sluneta in Ústí nad Labem, on 22 September 2018.^[11] She lost the fight by unanimous decision.^[12][13]

Castle faced Sutthinee Bamrungpao for the WIBA World Atomweight Championship on 26 October 2019, in Nonthaburi, Thailand. She won the bout by referee stoppage in the fifth round.^[14]