The Brazilian forward has struggled for first-team opportunities in recent months, with Rossoneri boss Massimiliano Allegri preferring to line up with the likes of Stephan El Shaarawy, Kevin-Prince Boateng, Mario Balotelli, M'Baye Niang and Giampaolo Pazzini in attack.
A return to his homeland has been frequently mooted for Robinho, who has a year left on his contract with Milan, but the Serie A club's CEO is in no doubt that the 28-year-old will stay put beyond the summer.
"Robinho is under contract at Milan and will stay. He's not going to leave. Anything is possible in football, but in principle he should remain in Milan," Galliani told Radio Gaucha.
"Internacional's interest? I'm aware of it, but now we are only thinking about qualifying for the Champions League."
Milan face Siena on Sunday, with a win guaranteeing them third place in Serie A and a spot in the upper European competition next season, as opposed to losing and potentially finishing fourth if Fiorentina win, meaning that they would play in the Europa League instead.