Wembanyama, who has had 41-point and 33-point outings in winning efforts during the series, never seemed to get fully rolling as the Spurs fell 3-2 behind in the best-of-seven series.
Shai Gilgeous-Alexander scored 32 points, while Alex Caruso led another strong bench effort with 22 as the Thunder moved one win away from a return trip to the NBA Finals.
Jared McCain - getting the call with Jalen Williams and Ajay Mitchell both sidelined - also scored 20 in his first playoff start for the defending champions.
- Latest NBA headlines, reports and highlights
- Not got Sky? Get Sky Sports or stream with no contract
- Choose the Sky Sports push notifications you want
It was a much improved performance from the Thunder, who were held to 82 points in a Game 4 loss two days earlier.
Oklahoma City went up by 20 in the third quarter, before San Antonio closed within eight. The Spurs might have had some chances to cut even further into the deficit, but were fuming - and rightly so, it seemed - over some missed calls in the final minute of the third.
The Thunder's lead was 101-91 going into the fourth and they kept a double-digit lead for all but 25 seconds of the final quarter - a huge turnaround from a 21-point loss in San Antonio on Sunday.
"We obviously played a lot better, in terms of our process and then also the outcome," Thunder coach Mark Daigneault said.
"It's a playoff series. If you look at any playoff series that goes to six games, at least, there's going to be some tough games.
"We had a tough game the other night. This team does a great job of just coming back in the next day in a very neutral way, taking whatever the lessons are, applying them forward and getting into the next opportunity."
Stephon Castle scored 24 points for San Antonio, with 22 points coming from Julian Champagnie and 20 from Wembanyama, who was held to 4-of-15 shooting.
"It just felt like it was a little bit of everything in terms of we did not put ourselves in position enough to be successful on each possession," Spurs coach Mitch Johnson said.
"And so, to beat a team of this calibre, in their building, with the stakes, we'll need to be a lot better to give yourself a chance."
Game 6 is on Thursday in San Antonio. If there's a Game 7, it'll be back in Oklahoma City on Saturday - with the New York Knicks waiting in the Finals, after disposing of the Cleveland Cavaliers inside four games on Monday night.
The Knicks will visit either the Thunder or Spurs in Game 1 of the NBA Finals on June 3.
Watch the NBA Playoffs live on Sky Sports. Not got Sky? Get Sky Sports or stream with no contract
