KuPS began the penultimate round two points clear of Ilves, and three clear of Inter Turku, who knew a defeat would end their dream of a first title since 2008.
Needing something from the match, the visitors began strongly, and took the lead just eight minutes in when KuPS failed to clear a corner, and Iiro Jarvinen ghosted into the box to slam the loose ball high into the roof of the net.
As the saying goes, late in the first half is "a good time to score", and this match in Kuopio proved that to be true. In added time, a hanging Jaakko Oksanen corner was headed in by Ibrahim Cisse, before KuPS took control in the second half.
Seven minutes after the break, Oksanen was again the provider with a free-kick curled into the area, and no FC Inter defender picked up Saku Savolainen at the back post, and he connected sweetly to put the reigning champions ahead.
Midway through the second half, KuPS added a third when Otto Ruoppi made his way to the edge of the box, and instead of taking the chance on himself, selflessly squared the ball to Piotr Parzyszek, who coolly rolled it into the bottom corner.
The Turku side gave themselves hope 10 minutes from time with a Florian Krebs penalty, but KuPS held on for the 3-2 win, going five points clear and eight games unbeaten, putting the long-time leaders out of the title hunt, as Inter Turku go three matches without a win at the most critical point in the season.
That meant not only were Ilves the only challengers left for KuPS, but the Tampere side had to beat SJK on Monday night to take the title race to the final day.
Like KuPS, Ilves also got off to a bad start, falling behind 17 minutes in when Lauri Laine drove through the heart of the home defence, played a neat one-two with Jeremiah Streng, and guided the ball home in real style.
Also like KuPS, the Lynx drew themselves level just before half-time - Marius Soderback got to the byline and pulled the ball back for Roope Riski to apply the simple finish.
However, unlike the Kuopio side, Ilves failed to kick on in the second half, falling behind again on the hour mark when Streng turned from provider to scorer, having been teed up by Kasper Paananen. But Ilves kept fighting, and were level again six minutes later through Oiva Jukkola.
Ilves looked to have finally ensured the title race went down to the last day when Riski scored his second of the game with nine minutes to play, only for the home fans' hearts to be broken deep into added time.
A long ball forward into the Ilves box was cleared only as far as Paananen on the edge of the area, he took it down, jinked past a couple of defenders and hammered the ball past Faris Krkalic in the Ilves goal to draw the match 3-3 and hand KuPS the title.
After triumphs in 2019 and 2024, it's a third league title this century for KuPS, whose previous five crowns all came between 1956 and 1976, and this marks the first time the club has won the league in back-to-back seasons.
For Ilves, the small consolation is that they have qualified for the UEFA Conference League for next season, while the only question left to be asked on the final day is who takes the final European place - Inter Turku or SJK, who are two points apart.
Nothing but local pride was at stake in the fourth and final Helsinki derby of the season, as sixth-placed Gnistan welcomed fifth-placed HJK for a share of the spoils.
Vertti Hanninen put Gnistan on course for a third win this season over their noisy neighbours, but Lucas Lingman and Santeri Hostikka turned things around with strikes before the break.
But HJK could not hold on, and in the 90th minute, Mihailo Bogicevic turned the ball into his own net to make it 2-2.
It's back-to-back draws for Gnistan, who remain 16 points behind HJK, who in turn stay seven points behind SJK. The only win either side has picked up in the Championship Group was the 3-2 win for Gnistan in the reverse fixture.