Benfica retained its Primeira Liga title after it was held to a goalless draw by Vitoria Guimaraes and Tiago Caeiro's late strike ensured Porto was held 1-1 at Belenenses.
A goal just before half-time from the prolific Jackson Martinez looked to have given second-placed Porto a victory that would have closed the gap to only a point with just one game remaining, but there was a late twist.
Caeiro came off the bench to equalise five minutes from time at Estadio do Restelo and ensure Belenenses's Lisbon rival Benfica secured back-to-back titles, becoming champion of Portugal for a 34th time.
Jorge Jesus's side was unable to secure a victory at the Estadio Dom Afonso Henriques, but a 0-0 draw against Vitoria Guimaraes was enough and it leads Porto by three points with a game remaining and is champion due to its head-to-head record against Julen Lopetegui's men.
Benfica celebrated in style on the pitch at the final whistle after learning that Porto had been denied by Caeiro, meaning it goes into this weekend's clash with Maritimo without the tension of the title being at stake.
Porto had won three titles in a row before last season, but it is now Benfica which has emerged as the dominant force in Portuguese football.
While Benfica will be toasting another title, Gil Vicente must prepare for life in the Segunda Liga after it was beaten 2-1 at already-relegated Penafiel.
Guedes put bottom side Penafiel in front just after half-time, but Joao Vilela gave the visitor hope when he levelled after 67 minutes.
A draw would still not have been enough to keep Jose Mota's charge up and David Mbala added insult to injury by scoring a winner in stoppage-time to seal its fate.
While the Barcelos outfit's four-year stay in the top tier is at an end, Arouca is safe despite slumping to a 2-1 defeat at fellow struggler Vitoria Setubal, which was also in danger of suffering the drop.
Academica was also in the mire, but can look forward to another season in the Primeira Liga despite a 3-2 loss at Pacos de Ferreira.
Adrien Silva scored twice as third-placed Sporting hammered Sporting Braga 4-1, while Maritimo dished out a 4-0 hammering to Rio Ave and Estoril drew 1-1 at Moreirense.