A try with the last play of the game from Jack Welsby earned St Helens the Super League title for the second straight year.
The best chance of the first half came from Wigan, as they found an overlap down the left-hand side, but desperate scrambling defence from Saints stopped Zak Hardaker from getting the ball down.
Saints took the lead with the last kick of the first half. Lachlan Coote took the two points after a shoulder charge on him by Morgan Smithies.
The champions had a great chance to score the first try. Zeb Taia got on the end of James Roby’s kick, but was adjudged to be offside.
Wigan finally got the first try after 66 minutes. Coote’s kick was charged down, gifting the Warriors field position. Tommy Leuluai then spread the ball to Jake Bibby, who slid in in the corner. Hardaker hit the crossbar with the conversion attempt.
Saints levelled again seven minutes later, Coote kicked the two again after an alleged high shot from Jackson Hastings on Theo Fages.
The Warriors then had the chance to win it, as Hardaker got a penalty from 40m out for interference by Fages, but missed.
Saints then came back up the pitch, and with the clock on zero, Tommy Makinson went for a drop-goal, which hit the post. Jack Welsby then beat Bevan French to the ball and scored to win it for the Saints.
It was the perfect way to send out the likes of James Graham, Zeb Taia and Dom Peyroux, who have played their final games for the club.
Saints have now gone back-to-back for the first time in 20 years.
As for Wigan, it was a disappointing way to end the season after finishing top, and may have thought they had done enough to win.