Conor McGregor will face lightweight champion Eddie Alvarez as he attempts to become the first UFC fighter to hold two belts at the same time.
Irishman McGregor, the 28-year-old featherweight champion, will meet American Alvarez, 32, at Madison Square Garden on 12 November.
It will be the first UFC event in New York after the city lifted its 1997 ban on professional mixed martial arts.
“This is the fight the fans wanted,” UFC president Dana White told ESPN.
BJ Penn and Randy Couture are the only fighters in UFC history to have won titles in multiple weight classes, although neither held more than one at the same time.
McGregor beat Nate Diaz in their welterweight rematch in August, having lost to the American in March.
UFC 205 will also feature defending welterweight champion Tyron Woodley against fellow American Stephen Thompson, while women’s strawweight champion Joanna Jedrzejczyk, from Poland, faces compatriot Karolina Kowalkiewicz.
White added: “This card has three world title fights and is the best card in UFC history.”