Keibler, 33, was the one who called things off "several weeks ago," a source tells People. "Stacy called it quits," according to the source. "She wants to have children and a family someday. She knows where George stands on that."
The breakup was amicable, according to People.
"They talk every day," the source says. "They were friends before they started dating and they'll be friends after."
Clooney, 52, is currently working on The Monuments Men, a World War II film that he directed and co-wrote, and also stars in. It is scheduled to hit theaters in December.