Sergio Conceicao’s players went into the game at the Estadio do Dragao needing only a point to end Benfica’s reign as champions.
But the hosts got off to a nervy start as Sporting forward Andraz Sporar saw a goal ruled out by the video assistant referee for offside in the first minute.
But after a barren first-half, Porto started to prepare the champagne in the 64th minute when midfielder Danilo Pereira headed home his second league goal of the season.
The Mali striker Moussa Marega launched the party celebrations with Porto’s second in stoppage time.
Conceicao’s second Primeira Liga crown in three years is as much due to his side’s grittiness as Benfica’s gormlessness.
Meltdown
At the half-way stage of 17 games, Benfica led Porto by seven points - a margin that had never been eroded in the 85-year history of the Portuguese top flight.
By the time the league was suspended as part of the government’s fight to stem the spread of the coronavirus pandemic, Porto led their arch rivals by one point with 10 games remaining.
But Benfica botched the resumption.
They could not capitalise on Porto’s loss at Famalicao on 3 June because they drew with Tondela on 4 June.
And even though both sides were level on points following the third round of games after the restart, Porto held the advantage due to their better head-to-head record with Benfica.
And they pressed home that lead with victories over Boavista and Pacos de Ferreira while Benfica imploded in losses to Santa Clara and Maritimo.
“The quality of football has been poor this season,” said Tom Kundert, editor of the Portuguese football website portugoal.net. “For example no Portuguese sides made it through to the latter stages of the Champions League.
“On a domestic level, Benfica have made some unwelcome history. No team has managed to lose such a lead and credit to Porto because they got the job done."
