The Rolling Stones frontman has been dating the fashion designer for the last nine years but insists he has no intention of making her his wife.
He tells the New York Times magazine, "I don't really subscribe to a completely normal view of what relationships should be. I have a bit more of a bohemian view.
"To be honest, I don't really think much of marriage. I'm not saying it's not a wonderful thing and people shouldn't do it, but it's not for me. And not for quite a few other people too, it would appear. I just think it's perhaps not quite what it's cracked up to be. I know it's an elaborate fantasy."
Jagger first married Nicaraguan actress Bianca Perez-Mora Macias in 1971 but they separated in 1977 when the singer began seeing model Jerry Hall, who he wed in 1990. His union with Hall was annulled in 1999.
Rachael Patan
Tagged in Sir Mick Jagger