Ronda Rousey knocked out by Holly Holm in UFC title upset

Holly Holm knocks out Ronda Rousey
Ronda Rousey (right) was the first American woman to win an Olympic judo medal - at the Beijing Games in 2008

Holly Holm stunned reigning champion Ronda Rousey to win the Ultimate Fighting Championship bantamweight title in Melbourne.

Rousey, 28, had won her previous 12 bouts and is considered the most feared female prize fighter in the world.

But fellow American Holm delivered a knockout head kick 59 seconds into the second round, plus several blows to the head, and the referee stopped the bout.

UFC pundit Joe Rogan called it the biggest upset in the sport's history.

It leaves multiple boxing world champion Holm, 34, undefeated in the mixed martial arts sport, with a 10-0 record.

UFC in focus
Mixed martial arts (MMA) in the UFC is comprised of many combat sports, including kickboxing, karate, jujitsu and wrestling.
You can defeat your opponent by either a judges' decision, referee's technical knockout, knockout, submission or forfeit

The event drew a record crowd of more than 56,000 at the Etihad Stadium.

Holm said: "I had so much love and support. I thought, 'how could I not do this?'.

"There was lots of blood, sweat and tears, but it sure was worth it. I'm trying to take this in, but this is crazy."

Holly Holm pins down Ronda Rousey
Holm (left) was considered the underdog in the bout
Holly Holm kicks Ronda Rousey
Holm delivered a head kick in the second round which floored Rousey
Holly Holm celebrates
Holm remains undefeated in her 10 career fights
Ronda Rousey recovers after her knock-out
Rousey required medical attention after her defeat on Saturday in Melbourne