52-year-old Shane Mosley hasn't fought in over 8 years, but the boxing legend's coming out of retirement -- for one fight, at least -- and the Hall of Famer is looking for a celebrity to share the ring!
TMZ Sports has learned "Sugar" -- last in the squared circle in May 2016 -- signed a contract with Celebrity Boxing ... and is gearing up for a return in late summer or early fall.
"I want to announce that we just signed to do an exhibition fight with the official Celebrity Boxing," Mosley said, adding, "I will be stepping back in the ring in August or September.