Marcus Fraser's close-range volley kept St Mirren in the William Hill Premiership as the Buddies beat Partick Thistle 1-0 in the play-off final.
The defender netted from a set-piece 20 minutes into the second half to seal a 2-1 aggregate win and extend the Paisley side's eight-year stay in the top flight.
Thistle enjoyed the better chances in the first half and pushed for an equaliser, but Saints goalkeeper Ross Sinclair made a breathtaking stop from Logan Chalmers' powerful free-kick.
Sinclair and Fraser proved unlikely saviours for the Buddies. The goalkeeper arrived on loan from St Johnstone last month following injuries to Shamal George and Ryan Mullen, while Fraser had been ruled out for the season after a shoulder injury before making himself available for the run-in against medical advice.
Championship runners-up Thistle must regroup following a fifth consecutive failed attempt to earn promotion through the play-offs and their second final defeat in that run.
St Mirren interim head coach Craig McLeish to Your Site:
"I'm delighted for the fans and the players. As a club, we shouldn't be in this position - we had to dig deep and get ourselves out of it. The game was the game, it's cagey and nervy - a game of mistakes and it's about who was going to capitalise on a moment. We did that.
"We have to build for next season and make sure this doesn't happen again. Delighted we got out of it, but don't want to be here again.
"It doesn't matter how we got it done, we just had to get over the line. We've done that in big moments all season.
"Absolutely [I want the job], everyone knows that by now. Whatever the club decide to do, I'm fine. I can't control those decisions. I stepped in at a difficult moment for the club. I've done everything we can to stay in the league. That was the remit when I got the role."
Partick Thistle head coach Mark Wilson to Your Site:
"That is sport at elite level, isn't it? When you get to the big games, there has to be a loser. We were on the wrong side of it tonight. Really tough because there's only one goal in it, a set-piece at that.
"It's cruel when you get to the end of the season, so much has been to it in 52 games. You could see every one of the players put their heart and soul into it. It's going to be a tough one to take, it's important to remember it and come back stronger next year.
"Everybody has to remember where we were when we got appointed last year - a broken squad and a lot of players leaving. Whatever happened tonight, we're well ahead of the curve. It really raw and sore just now, but I was just saying to the guys: what they've achieved in one season is quite extraordinary. That was just our seventh defeat in 52 games."
