The Bulls (8-7, 1-1 American) also got 12 points and nine rebounds from Michael Durr.
James Bouknight had 11 points for UConn (9-5, 0-2 American), which was coming off a 67-51 loss at Cincinnati on Wednesday night in the conference opener.
UConn got within 12 with eight minutes remaining but Rideau's layup completed a 7-0 run that made it 70-51.
Justin Brown put USF ahead 53-38 on a 3-pointer with 15 1/2 minutes to play.
South Florida went 21 of 29 from the free-throw line. UConn made 10 of 16.
Rashun Williams extended the Bulls lead to 61-42 midway through the second half. That surge came during a four-minute scoreless stretch by UConn.
Rideau had 13 points as USF took a 39-32 halftime advantage. He had a 3-point play and added a layup during a 12-2 run that put the Bulls up 39-29.
Alterique Gilbert cut the UConn deficit to seven on a long-range jumper with 9 seconds left in the first half.
UConn: It was a rare loss in the all-time series between the teams. The Huskies have won 22 of the 26 overall meetings.
USF: Rideau has had success against UConn. In three previous games, the senior guard averaged 17.7 points and six rebounds.
UConn: Has its conference home opener against Tulane on Wednesday night.
USF: Play Tuesday night at East Carolina.
For more AP college basketball coverage: https://apnews.com/Collegebasketball and http://twitter.com/AP-Top25
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