Conor McGregor is the first fighter in UFC history to hold titles in multiple weight classes at the same time.
The brash Irishman has knocked out lightweight champion Eddie Alvarez in the second round of their UFC 205 headliner.
Alvarez was battered from the get-go and never got in a groove as McGregor quickly established range with his trademark left hand.
The knockout came late in the second round - the fifth knockdown of the fight proving to be the end of Alvarez short title reign.
The next move for the new champion is to be determined, with the options being a rematch with Jose Aldo for the featherweight title or a murderers' row of contenders at his newly found division.
McGregor was as outspoken as ever in the post-fight interviews, claiming that no fighter alive belongs in the cage with him.
Elsewhere, Tyrone Woodley and Stephen Thompson fought to a draw in the fight of the night for the welterweight strap, and Joanna Jedrzejczyk shut-down t Karolina Kowalliewicz, with a unanimous decision won to retain her women's straw weight championship.