Renan Barao, the
UFC President Dana White finalized the bout as a replacement for the postponed middleweight title defense by champion Chris Weidman against former light-heavyweight champion Lyoto Machida.
Weidman last week suffered a knee injury that required minor surgery. Weidman-Machida will now be fought in July at Mandalay Bay in Las Vegas.
The 27-year-old Barao (34-1) won the belt in July 2012 by defeating veteran Urijah Faber and has successfully defended the belt three times, most recently by a first-round technical knockout of Faber in February.
Sacramento's Dillashaw (10-2) is the UFC's No. 5-ranked bantamweight. He responded to an October split-decision loss to No. 3 Raphael Assuncao by beating Mike Easton by unanimous decision in January.
The May 24 card also includes a heavyweight fight between former champion Junior Dos Santos and seventh-ranked Stipe Miocic (11-1).