There has been constant speculation suggesting the Italian could join the San Siro giants throughout the current transfer window.
The noises coming out of Italy tend to vary but after suggestions Milan had been priced out of a permanent deal for the 22-year-old, there are now reports he could move on loan.
But Mancini said: "It is not true, Mario stays here. We didn't have any requests about Mario or other players."
Mancini has maintained this firm line on the possibility of Balotelli leaving the Etihad Stadium, even after a training-ground bust-up with the player earlier this month.
Milan are interested in the forward with vice-president Adriano Galliani issuing regular statements on the possibility of a deal but the club are unwilling to meet City's reported £28million valuation.
Galliani has urged City to lower the price but Mancini says he has no intention of letting his former Inter protege leave, even on loan.
When asked if Balotelli was part of his long-term plans, Mancini said: "Yes, Mario has another three years on his contract."
Mancini was speaking at a press conference to preview his side's FA fourth-round tie at Stoke.
The Balotelli subject was the first to be discussed.
Mancini said: "For two years, the first question is always Mario!"
The transfer window closes next week but Mancini is not anticipating much activity.
He said: "I don't know but we don't have enough players. We are 18 players now. We can't sell any players."
When asked on the possibility of players coming in, Mancini said: "I think it is difficult."
Mancini has also been surprised by reports that director of football Txiki Begiristain wants the club's teams to play in a fluid 4-3-3 system from next season.
Begiristain enjoyed conspicuous success with such a style when in an equivalent role at Barcelona.
Mancini claims this is not something he has discussed with Begiristain, who took up his post at City last autumn.
The Italian said: "I don't know. I speak with Txiki every day and he never told me this. We have the same thoughts about football.
"I don't think it is more important to play 4-3-3, 4-4-2 or 4-1-5, it is more important to have good players."
Mancini is a huge admirer of Barcelona but does not think it is that easy to copy them.
"It is impossible to play like Barca but I think that you can win also if you play a different style."
Mancini claims he does not have any differences with Begiristain over footballing philosophy.
He added: "We are agreed about everything because we think the same. About football we are the same, we don't have differences."