The Seminoles (7-0) also extended their winning streak against the Gators (5-2) to four, their longest in the 68-game history of the series.
Florida State's length and athleticism posed problems all night. The Seminoles altered shots, forced turnovers, controlled the boards and didn't allow Florida many clean looks, especially from long range.
Coach Mike White pleaded with his Gators to be more physical at halftime, but they didn't respond. Now, Florida has a two-game losing streak and questions about their lofty ranking.
White said his team's performance was "the epitome of soft."
"We spent the last 24 hours talking about throwing the first punch, throwing the first punch, being the aggressor, being proactive against a team that's gotten the better of us the last few years," White said. "They threw the first three or four punches and continued throwing most of them and connecting on most of them until the final buzzer. A very disappointing effort."
The Gators entered the game with the nation's top offense, having averaged 99.6 points in their first six games. But they went cold down the stretch against top-ranked Duke in the Phil Knight Invitational in Portland, Oregon last week, and never found a rhythm against the Seminoles.
Florida blew a 17-point lead with 10 minutes left against the Blue Devils and lost 87-84. Big man Marvin Bagley III dominated Florida inside in that one.
The 6-foot-6 Mann was the main culprit Monday.
Mann made 11 of 17 shots and added eight rebounds. Every time Florida looked like it would make a run, Mann answered on the other end. The junior had a tip-in and two three-point plays in the final 8 minutes.
With Mann leading the way, Florida State outrebounded Florida 51-34, including 23-11 on the offensive glass. The Seminoles also outscored the Gators 36-20 in the paint and 12-2 on fast breaks.
"They out-toughed us from the start, from the jump," Gators guard Jalen Hudson said. "It's super humbling. We're definitely not as good as we think we are. We're definitely not as good as the rankings say. ... I don't think we had the greatest week this week. I think we were too celebratory in the PK80. We did some good things out there. It's two losses in a row. It's unacceptable."
Hudson (16 points), KeVaughn Allen (15), Egor Koulechov (11) and Chris Chiozza and were a combined 13 of 40 from the field, including 4 of 20 from 3-point range. Chiozza was scoreless until making three free throws down the stretch.
Equally troubling for the Gators: A season-high 17 turnovers.
Florida: The Gators are in survival mode until 6-foot-11 center John Egbunu returns from a knee injury. Egbunu averaged 7.8 points and 6.6 rebounds last season before tearing a ligament in his left knee at Auburn in February. The senior is expected to return in mid-January, and Florida believes he will again be an imposing force in the paint. Egbunu holds the school's single-season record for dunks (75 in 2015-16). In the meantime, the Gators are trying to compete with a four-guard lineup and no physical threats down low.
Florida: Hosts Loyola-Chicago on Wednesday.