The chef and the general manager who five years ago opened Grace, a Chicago restaurant considered one of America’s best places to dine, have quit after a dispute with the wealthy Chicago real estate investor who owns it.

The loss of the two men — the chef Curtis Duffy and Michael Muser, the general manager, who also ran the wine program — leaves the future of the restaurant in limbo. Under their guidance, Grace became one of only 14 restaurants in the United States to win three Michelin stars.

“This is going to shake the restaurant community to the core,” said Carrie Nahabedian, the chef who runs Naha, a Chicago restaurant that also has a Michelin star, and is close to the two men.

Ms. Nahabedian and Kevin Pang, a former reporter for The Chicago Tribune who was the co-director of “For Grace,” a 2015 documentary about the restaurant, said the men’s departure came after a contract dispute with Michael Olszewski, the investor who provided more than $2.5 million to open Grace. Mr. Olszewski did not return calls seeking comment.