Galliani admitted the Los Angeles Galaxy are keen on the 30-year-old, who has another year to run on his contract, but claims he is not for sale.
"Ronaldinho is a Milan player. Milan won't transfer him and moreover he has never asked to be transferred," the Milan chief told Gazzetta.it in a videochat.
"So he will remain at Milan for the next season at least but I hope for many, many more years.
"It's true Galaxy are interested in him. After David Beckham, they want another star but Galaxy will have to wait for many more years.
"There is absolutely no possibility that Ronaldinho leaves. His brother/agent is a friend of mine who I courted for two years before Ronaldinho started with us. I will meet him in the upcoming months especially to extend Ronaldinho's contract, certainly not to discuss his departure."