The 23-year-old has been the subject of Chelsea transfer rumours recently, despite the Italian not enjoying the best of relationships with Blues manager Jose Mourinho.
The pair first worked with each other at Inter Milan, and didn't enjoy the closest of friendships.
And with talk of Milan's star player leaving the San Siro, Galliani quickly moved to quash the rumours.
"Mario Balotelli will not leave Milan," he is quoted as saying on Goal.com.
"He will stay with us for many years, and he is our star. He has a long contract and he will see it out."
Balotelli's former club - rivals Inter - have recently been the subject of a potential takeover from billionaire Erick Thohir, although Galliani dismissed the possibility of a similar move taking place at AC.
"There has been no kind of contact whatsoever, because the club is not for sale. Even more so now that the accounts are matched," he said.
Milan have had an appalling start to the season, and after nine games linger in 10th.
With Roma in sensational form, the Rossoneri are already 16 points off the pace.
However, the vice-president gave his backing to manager Massimiliano Allegri, saying he will remain in charge until at least the end of the season.
"Allegri will remain our coach," he added.
"At the end of the season we will see how things have gone and assess our options then.
"I spoke with [Riccardo] Montolivo and told him that, as captain, I expect better. I was also unhappy with [Valter] Birsa, who I expect to see play as well on Saturday's and Sunday's as he does in training."
With Balotelli now apparently off the radar, Chelsea may turn their attentions to Robert Lewandowski who is available to talk to foreign clubs as of January.