The Bellator card is scheduled for June 14 in New York.
Sonnen (30-16-1) will return to the light heavyweight division after going 1-1 as a heavyweight, defeating Quinton Jackson and losing to Fedor Emelianenko in Bellator’s grand prix. In his last appearance at 205 pounds, Sonnen defeated longtime rival Wanderlei Silva.
Machida (25-8) is riding a three-fight winning streak, including a pair of UFC victories over Eryk Anders and Vitor Belfort before joining Bellator and defeating former middleweight champ Rafael Carvalho via decision in his debut.
“The Dragon” holds wins over current Bellator titleholders Gegard Mousasi, the middleweight kingpin, and two-division champion Ryan Bader. The Brazilian star hasn’t competed at light heavyweight since losing a decision to Phil Davis in Aug. 2013.