Helsingborg have an unassailable 61 points, 10 more than AIK Stockholm who were held to a 1-1 draw at Malmo.
Elfsborg, the only other club able to catch the leaders, suffered a surprise defeat at Mjallby on Saturday.
Helsingborg went ahead against GAIS in Gothenburg through Erlend Hanstveit’s first-half goal but the hosts levelled from the penalty spot shortly after the break.
Striker Erik Sundin fired the leaders ahead again against the run of play and Rachid Bouaouzan netted a late penalty to seal victory.
That win put the pressure on AIK, the only side left with a theoretical chance of snatching the title, who had to win in the late kickoff against Malmo, Helsingborg’s fierce local rivals.
The Stockholm side dominated possession and when Niklas Backman scored in the 84th minute it looked like being enough to keep the race going for at least another week.
But Mathias Ranegie’s injury time strike ended their slim hopes.
