De Minaur put up some major resistance to Sinner in the first set on Saturday, not only bringing up triple break point in the Italian's very first service game at 0-1, 0-40, but fighting off all five break points he faced himself in his first five service games en route to 5-all.
But Sinner stepped it up from there, reeling off six games in a row for a 7-5, 4-0 lead, and the two held from there until it was over.
And with that win, not only is Sinner now 13-0 in his career against De Minaur, he's now won 18 sets in a row at the ATP Finals, 30 matches in a row on indoor hard courts and 59 service games in a row.
That service streak dates back to the quarterfinals in Paris.
He's also through to his third straight ATP Finals final, having finished runner-up in 2023 (to Djokovic) and winning the title in 2024.
"I'm very happy. Last event of the year, great to finish in this way," he said. "It was a very tough match today, especially in the beginning of the first set—I felt like he was serving great, very precise. In the second set I got the break very early and then my level increased, and I tried to be a bit more aggressive, which worked very well.
"But making three consecutive finals here means a lot to me. It's a great atmosphere for me to play tennis, and it's a great place for me to close this beautiful season that I've played in."