The main event pits Lyoto Machida against Rampage Jackson in a three round event live from Detroit.
Both top fighters were former UFC light heavyweight champions with dreams again of holding the belt.
Rampage last lost to Rashad Evans after filming the A-Team movie.
Machida lost a rematch to Shogun Rua where he was knocked out in the first round.
See below the UFC 123 Fight Card and Weight-in results:
Quinton “Rampage” Jackson (205) vs. Lyoto Machida (205)
Matt Hughes (169) vs. B.J. Penn (169)
Tim Boetsch (205) vs. Phil Davis (205)
Joe Lauzon (155) vs. George Sotiropoulos (155)
Maiquel Falcao (185) vs. Gerald Harris (185)
Matt Brown (170) vs. Brian Foster (170)
Mark Munoz (185) vs. Aaron Simpson (185.5)
Dennis Hallman (170) vs. Karo Parisyan (170)
Edson Barboza (155) vs. Mike Lullo (155)
Paul Kelly (155) vs. T.J. O’Brien (155)
Nik Lentz (155) vs. Tyson Griffin (155)