The actress, 33, is in London to address the House of Commons on Wednesday for the domestic violence charity initiative Refuge in partnership with Avon, which Witherspoon represents.
Meanwhile, Gyllenhaal, 28, has been shooting the upcoming drama Love and Other Drugs in Pittsburgh.
A source told PEOPLE that Witherspoon had informed her friends over the Thanksgiving weekend that she and Gyllenhaal had ended their two-year relationship.
But another source maintains that the pair are still together. Was there a recent break up? "Not officially," says the source.
Reps for both stars have also denied a split.