The win gives Mercer (14-4, 4-1 Southern Conference) five wins in its last six games.
Ringer made a layup with eight seconds left in regulation to tie the score at 64 and send the game to OT. Wofford (7-11, 4-2) scored five of the first seven points of the extra period on the strength of a Spencer Collins 3-pointer and two Eric Garcia free throws to take a 69-66 lead.
But Phillip Leonard hit a jumper for the Bears with 1:18 to go and after Collins missed a 3 on the ensuing possession Ringer hit the game-winner.
The Terriers had a final shot, but Collins missed again from deep.
Jestin Lewis scored 18 points for Mercer. Collins had a career-high 30 points for Wofford.