The A-list actor met Stacy - a retired professional wrestler - back in 2011 and the couple became inseparable, attending award ceremonies and red carpet events together.
However, in recent months the two stars are said to have been "falling apart" and realising that there is no real future for their relationship, which has apparently caused them to amicably break up.
A source told Us Weekly: "Stacy knew George was not the man to settle down with... They know this is for the best."
According to the insider, Stacy, 33, and George, 52, agree that the split was the right decision, especially since they've both been working hard on solo projects in different countries lately and barely have time to spend together.
Stacy and George have not confirmed the split yet.
Sources previously told the publication that Stacy had also been starting to feel the age difference between herself and the Ocean's Eleven actor.