Reserves Darrione Rogers scored 19 points and Mjracle Sheppard added 12 as Mississippi State used a strong defensive effort in the third quarter to beat No. 9 LSU 77-73 on Monday night.
The loss was the second straight for LSU, which fell to top-ranked South Carolina 76-70 on Thursday. It was the third loss in five games for the Tigers (18-4, 5-3 SEC).
"This game was one that was not surprising. When you play a game on the road after a big game like we had with South Carolina, you watch your team and see how they reacted," LSU coach Kim Mulkey said. "We had the lead and did some things early, but in the second half we can't seem to get stops defensively when they matter. You have to get stops at this level, and we don't seem to be doing it."
LSU became the second defending national champion in the past decade to lose back-to-back games, according to ESPN Stats & Information. The other was 2017-18 South Carolina, which lost to UConn and Mississippi State.
Mississippi State snapped a 15-game losing streak against AP Top 25 teams, winning its first such game since March 7, 2020, at No. 16 Kentucky.
JerKaila Jordan scored 15 of her 24 points in the second half for Mississippi State (17-5, 4-3).
Sheppard, who held LSU All-American guard Hailey Van Lith to four points, added 6 steals, 5 assists and 4 rebounds. Rogers shot 6-for-10 from the field, including four 3-pointers, and hit three key free throws in the final 30 seconds.
"Those are those moments that you dream about as a kid -- big situations against top teams," Rogers said. "My teammates and coaching staff truly believe in me, and they get mad when I don't shoot the ball. I live for those moments."
Angel Reese had 20 points and 18 rebounds for LSU. Flau'jae Johnson finished with 18 points on 8-of-11 shooting, Aneesah Morrow scored 14 points and Mikaylah Williams 11.
Rogers hit a 3-pointer with about a minute left in the game to end a nearly six-minute scoring drought for Mississippi State, extending the Bulldogs' lead to six points and helping to seal the win.
Mississippi State trailed by two points entering the second half before seizing control in the third period. LSU missed its last nine shots in the third, and the Bulldogs used a 28-point outburst to take a 63-57 lead with one quarter remaining.
The Bulldogs extended their lead to nine points with about five minutes remaining. LSU closed within three points before Rogers hit a 3-pointer to provide a bit of breathing room.
Mississippi State made 53% of its shots, hitting 30-of-57 from the field with 9-of-17 shooting from 3-point distance. The Tigers were at 45% (29-of-65) and just 3-of-14 from long range. The Bulldogs got 35 points from their bench, while LSU got six.
"I'm a man of words, but I'm still speechless," MSU coach Sam Purcell said. "This is what I dreamed about. This is the moment that I wanted to come here. I told everyone to give me a chance, but give us a chance together. This place is special."
The Associated Press contributed to this report.