Terence Crawford and Viktor Postol, both unbeaten 140-pound champions, will meet in a title unification fight July 23 in Las Vegas.
Promoter Bob Arum announced the bout at a news conference Tuesday in Los Angeles.
Both fighters are 28-0 and will put their title belts and unbeaten marks on the line in a scheduled 12-round fight from the MGM Grand arena.
Crawford, of Omaha, Nebraska, has won four of his last five by stoppage. The 2014 fighter of the year by the Boxing Writers Association of America will be making his third defense of the WBO version of the title.
Postol, who is from Ukraine, is coming off the biggest win of his career. He stopped heavily favored former world champion Lucas Matthysse in October to win the WBC belt.
The fight will be televised on pay-per-view.