The Tigers' junior forward was 12-for-20 from the field, pulled down nine rebounds and blocked two shots in a dominant all-around performance on a night when a rare winter storm struck the Southeast.
"The kid wanted to come out and play hard against Kentucky, and he did that. He dominated," Kentucky assistant coach Kenny Payne said of O'Bryant, a one-time UK recruiting target.
LSU (13-6, 4-3 SEC) also got 14 points and five blocked shots from freshman forward Jordan Mickey, much to the delight of an estimated crowd of 6,000 who fought through the ice and snow to see a memorable game at the Maravich Center.
Freshman guard James Young scored 23 points for Kentucky (15-5, 5-2 SEC). The Wildcats also received a career-high 15 points from freshman center Dakari Johnson off the bench, but those were the lone bright spots for the visitors.
UK got only nine points and 11 rebounds combined from starting big men Willie Cauley-Stein and Julius Randle. Twin guards Andrew and Aaron Harrison had 22 points, but nine of those came in the final 42 seconds on a flurry of 3s by Aaron Harrison. Andrew Harrison had just one assist in 35 minutes of action at point guard.
The Tigers shot 51 percent on the night, made seven of 18 from 3-point range and dished out 15 assists. LSU also dominated on the defensive end of the floor, holding UK to 44 percent from the field, blocking 11 shots and recording 11 steals that helped lead to 16 points off turnovers.
"Very disappointing for our players, very disappointing for our coaching staff," Payne said. "We gave them a game plan, and they didn't come out and execute. But more importantly, we didn't come out and fight. Some of these games, it's all about fight. It's not strategy, it's not Xs and Os, it's not who's got the better players. It's who's going to fight? We didn't come out and fight."
LSU pounced on a dazed UK squad for a 22-6 lead in the game's opening minutes. It marked the largest deficit the Cats have faced in a game this season.
Kentucky recovered with a 13-3 run to pull within 25-19 with 7:44 remaining in the first half and pulled within two at one point, but trailed 42-36 at the break.
The Tigers never relinquished their lead, building the margin to 15 late in the game before UK hit four 3-pointers in the final 65 seconds to leave town with a deceptive final score.
* Kentucky leads the series 83-25, including 29-17 in Baton Rouge, but LSU got its first win in six games versus a John Calipari-coached UK team.
* UK is 44-10 all time as the AP No. 11 team, but three of tohse losses have come under Calipari.
* The Wildcats return to action on Saturday at Missouri. Tip is slated for 1:30 p.m. ET on CBS.