Molde lead the Tippeligaen on 56 points, with Stromsgodset a point behind and Rosenborg four points adrift with two games left to play.
Unfancied Stromsgodset, with only one league title to their name, recovered from a goal down to beat 22-time champions Rosenborg, with Peter Kovacs heading the winner 15 minutes from time.
"We had great team spirit, and we won a very precious victory," Kovacs told Norwegian TV. "We came from behind against a very good Rosenborg side. It's a great achievement."
As Rosenborg found to their cost, there was no room for slip-ups on a weekend where the top four all met each other.
On Saturday, Molde played out a cagey 1-1 draw against fourth-placed Tromso and it was equally tense in the first half at Stromsgodset on Sunday.
Rosenborg looked like keeping the pressure on Molde when Swedish striker Rade Prica put them ahead in the 64th but Ola Kamara volleyed an equaliser three minutes later and Kovacs headed home a corner in the 76th.
"We've gone five games without losing now," Stromsgodset coach Ronny Deila told newspaper Verdens Gang, adding that although the fate of the title was in Molde's hands, his side would push them all the way.
"Molde are good. It's not a case of simply going and collecting points in the last two games. If both sides take six points and Molde win, they'll have deserved it.
"Then I'll congratulate them - but it will be a fantastic fight, right to the end," said Deila.
Both sides face slightly easier games next week, as Molde travel to 12th-placed Honefoss and Stromsgodset take on Sandnes Ulf, who are second from bottom of the 16-team league.