LSU (13-3, 2-1 Southeastern Conference) dominated in the paint with its talented frontcourt of Jordan Mickey and Martin. Mickey finished with 11 points and 11 rebounds.
The Tigers' guard play wasn't bad either. Hornsby nailed five 3-pointers and Josh Gray finished with 14 points and 10 assists.
LSU broke a three-game losing streak against the Rebels. It's the first time the Tigers have won in Oxford since 2009.
Ole Miss (10-6, 1-2) led for a big chunk of the first half, but couldn't overcome a bad shooting night by its starting guards. Leading scorer Stefan Moody made just 5 of 18 attempts from the field to finish with 14 points.
M.J. Rhett led Ole Miss with 15 points.
The game was tight throughout the final minutes, but LSU made enough free throws — including two by Hornsby with five seconds left — to keep Ole Miss at arm's length.
Ole Miss opened the game in control and pushed its lead to 26-19 on a Jarvis Summers jumper with 4:28 remaining in the first half. But the Tigers closed on a 13-2 run, capped by Hornsby's 3-pointer from the corner to give LSU a 32-28 halftime advantage.
The Rebels used a 12-0 run to take a 44-43 lead on LaDarius White's 3-pointer with 13:49 left, but LSU didn't panic, using a mix of Mickey and Martin down low and timely outside shooting from Hornsby, who hit 5 of 10 from 3-point range.
The 6-foot-10 Martin was especially efficient, making 9 of 12 shots from the field and controlling the glass.
It was a third straight difficult game for LSU, which lost to Missouri in overtime last week before needing double overtime to beat Georgia.
Summers scored 13 points for Ole Miss while Dwight Coleby added 10 points and eight rebounds. Ole Miss shot just 27 of 78 (34.6 percent) from the field.
LSU: Tim Quarterman scored eight points one game after scoring a career-high 27 points in the Tigers' double overtime victory on Saturday. Quarterman has scored 54 points in three SEC games.
Ole Miss: The Rebels came into the game leading the nation in free-throw percentage, making 79.1 percent of their attempts. Ole Miss made 12 of 16 (75 percent) on Wednesday.
LSU hosts Texas A&M on Saturday.
Ole Miss travels to face Arkansas on Saturday.
AP: LSU 75, Ole Miss 71
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