With the game seemingly set for a draw, the substitute turned the Primeira Liga table on its head
The 19-year-old prospect came off the bench to great effect by netting an emphatic strike in the last minute, taking his side a crucial point clear ahead of Jorge Jesus' men in the league standings, with just one game remaining.
"My happiness is huge, and I thank God for everything," the Brazilian talent gushed to Sport TV after the match. "It was a historic goal for me, I'm just starting my career.
"I got the pass from Liedson, I controlled and shot with my left. The coach asked for the same thing from me as against Sporting Braga. I got away from my marker well and scored the goal.
"You can watch our games, and everything we have done is deserved. There is one game to go to seal the championship. Now we will focus on the game against Pacos de Ferreira."
Kelvin has now managed three goals in seven appearances for Porto since joining them from Parana.
The defending champions are in the driving seat to win their third consecutive title, having gone the entire season unbeaten.