UFC 173: Barão vs. Dillashaw was a mixed martial arts event held at the MGM Grand Garden Arena in Las Vegas, Nevada on May 24, 2014.

A Middleweight Championship bout between then champion Chris Weidman and number one contender Vitor Belfort was scheduled to headline this event.

[3] However, on February 27, the Nevada State Athletic Commission officially banned testosterone replacement therapy (TRT) from combat sports.

The main event was quickly changed as former UFC Light Heavyweight Champion Lyoto Machida agreed to step in to face Weidman for the title.

[10] Subsequently, the bout between Dan Henderson and Daniel Cormier, briefly linked to UFC 175[11] was moved up to this event to bolster the card.