Which fighter defeated Brock Lesnar by submission at UFC 81?

Frank Mir defeated Brock Lesnar by submission at UFC 81.

The bout took place on February 2, 2008, in Las Vegas, Nevada. Lesnar controlled much of the opening exchange with his size and wrestling, but Mir used a kneebar to force the submission in the first round.

The victory was especially notable because it was Lesnar’s second professional mixed martial arts bout and his UFC debut. Mir’s technique demonstrated how a submission specialist could capitalize on a momentary positional mistake against a much larger wrestler.

Lesnar later became UFC heavyweight champion, while Mir remained one of the division’s most accomplished submission artists. This fight is sometimes confused with their rematch at UFC 100, which Lesnar won by technical knockout.