First athlete to win a boxing and MMA world title
Holly Holm
First first
Australia (Melbourne)

The first athlete, male or female, to be both boxing world champion and a MMA (Mixed Martial Arts) world champion is Holly Holm (USA, b. 17 October 1981), who became WBA welterweight champion in 2006 and held world titles until 2013. She became UFC Bantamweight champion by defeating Ronda Rousey (USA) by way of second-round knockout in Melbourne, Australia, on 14 November 2015.

Holm caused a huge shock in Melbourne to become the first person to defeat Ronda Rousey in her 13th UFC fight; previously only one person had managed to survive the first round against Rousey an Olympic bronze medallist in Judo. It was described as one of the biggest upsets in MMA history.