A stoppage-time goal from substitute Kelvin handed Porto a 2-1 home win over fierce rivals Benfica on Saturday that put them on the verge of clinching a third consecutive Portuguese league title.
The two teams were undefeated going into the penultimate game of the season and victory gave leaders Porto a one-point advantage over second-placed Benfica.
The majority of the Dragao stadium's 50,000-capacity crowd were ecstatic at the final whistle while visiting coach Jorge Jesus sank to his knees in disbelief when 19-year-old midfielder Kelvin struck with a fierce, diagonal left-foot shot.
Porto had most of the possession in a cagey affair but Benfica, who meet Chelsea in the Europa League final in Amsterdam on Wednesday, scored from their first chance in the 20th minute.
A long throw-in caused havoc in the home defence and Lima fired in from close range after pouncing on an Ezequiel Garay shot that skewed off a defender.
Porto hit back five minutes later when Silvestre Varela's low cross deflected off Benfica right back Maxi Pereira and into the net.
The champions travel to third-placed Pacos de Ferreira in their last fixture while Benfica host second from bottom Moreirense.