Madrid have brought in Jude Bellingham, Joselu, Fran García, Brahim Díaz and Arda Güler this summer, with €103 million ($112m) Bellingham making an instant impact with three goals in two LaLiga games.
However -- with Joselu their only senior centre-forward -- Madrid have also been repeatedly linked with long-term target Mbappé, who was frozen out by Paris Saint-Germain when he said he would not stay there beyond 2024, before being brought back into the squad last week.
"I rule it out. 100%," Ancelotti said in a news conference on Thursday, when asked if he expected any arrivals before the window closes on Sept. 1.
The make-up of Madrid's squad, with Spain international Joselu and Brazilians Vinícius Júnior and Rodrygo Goes in attack and eight senior midfielders, has seen Ancelotti drop his usual 4-3-3 formation for a 4-4-2 with a midfield diamond.
That system has got the best out of Bellingham as a No. 10, scoring twice and providing an assist in Madrid's 3-1 win at Almeria on Saturday.
The competition for places in midfield has seen Luka Modric relegated to the bench so far, but Ancelotti said he didn't fear the former Ballon d'Or winner would push for an exit, with the transfer window in Saudi Arabia open until Sept. 20.
"I think Luka has already chosen what wants to do for the next year," Ancelotti said. "It's true that it's an unusual situation for him. He isn't playing as he's used to in this moment of the season, because there's just one game a week.
"He isn't happy obviously but he's fine, he has no problems, and he'll contribute."
Ancelotti was asked about Spanish football federation president Luis Rubiales, whose behaviour after Spain's World Cup win -- kissing forward Jenni Hermoso on the lips -- has sparked international outrage and calls for Rubiales to lose his job.
"It's a delicate subject," Ancelotti said. "But as a citizen, like most people I think, it was behaviour that I didn't like... His behaviour wasn't the behaviour of the president of the federation."
Madrid travel to Celta Vigo with their opponents -- coached by former Madrid boss Rafa Benitez -- celebrating their 100th anniversary this week.