Kunis, a former cast member of "That 70s Show," has been earning accolades for her work in the big-screen psychological thriller "Black Swan," which is set in the ballet world.
Culkin was the star of the iconic "Home Alone" movies.
Kunis and Culkin dated for about seven years.
"The split was amicable, and they remain close friends," Kunis's representative told the New York Post.
The reason for the relationship's end was not disclosed.
The Post quoted an unnamed source as saying the couple split up a while ago but didn't want news of the breakup to take away from the personal appearances and interviews Kunis had been doing to publicize "Black Swan."