The actor's rep, Stan Rosenfield, would only say: "We do not comment on George's personal life."
The pair initially met in Las Vegas nearly four years ago, when Larson, a onetime Fear Factor winner, was a cocktail server at The Whiskey Bar. But it wasn't until the pair met for the second time in June 2007 in Las Vegas that sparks flew.
Larson, 29, and Clooney, 47, made their public debut together at the Venice and Deauville film festivals last September. Later that month, the twosome were injured in a motorcycle accident.
Earlier this year, Larson accompanied Clooney to the Oscars – the first girlfriend ever to go with him to the event.
Though there was speculation that Clooney would end his longtime bachelorhood, in March the actor shot down rumors of an engagement.
Next up for Clooney is the Coen brothers movie Burn After Reading, co-starring Brad Pitt, due out in September.