Fati came off the bench at the San Siro, to score in the 87th minute to seal a 2-1 victory.
Aged 17 years, 40 days old, with this goal Fati takes the record from Peter Ofori-Quaye, who was 17 years, 194 days old, when he scored his first Champions League goal for Olympiacos in 1997.
“I’ve just been told [I have broken the record]. I am super happy with the goal and with the win,” Fati told reporters after the match.
“It’s a dream. Everything seems to be happening so quickly. It’s just about enjoying myself and learning from the best. Every time I get a chance, I will try to take it, either by scoring goals or by working hard.”
Describing the goal, Fati said: “I gave the ball to Suarez, and he gave it back to me. And when I scored, I was surprised because the whole stadium was silent. I was thinking: ‘What have I just done?’ But I am really happy.”