Gene Hackman acted in self-defence when he slapped a homeless man who became aggressive with the actor and his wife, police have said.
The Albuquerque Journal reports that the incident occurred on Tuesday in the centre of Santa Fe, New Mexico, where the couple have a home.
Police did not immediately provide any additional details and Mr Hackman's publicists at Guttman Associates in Beverly Hills have not provided any comment.
The 82-year-old actor has won two Academy Awards and been nominated for three others over a career that has spanned five decades.
Hackman took the Best Actor trophy for his portrayal of Jimmy "Popeye" Doyle in The French Connection in 1971, and the Best Supporting Actor award for Unforgiven in 1992.