Her New York-based publicist, Robert Garlock, says the couple -- who have been together on and off for three years -- are no longer an item.
"I confirm that they are no longer a couple," Garlock said Monday.
Thurman, 36, received an Oscar nomination for 1994's "Pulp Fiction." She has also starred in two "Kill Bill" movies.
She filed for divorce from Ethan Hawke in 2004. They have two children.