Larson was at Clooney's side when he was making the premiere and awards show rounds for his 2007 legal drama "Michael Clayton."
The former waitress and "Fear Factor" winner was also with him when he was hit by a car while riding his motorcycle in New Jersey last year. He fractured a rib while she broke a toe.
Clooney's spokesman Stan Rosenfield wouldn't confirm the split, telling People: "We do not comment on George's personal life."
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