“That ’70s Show” star Mila Kunis left her boyfriend “home alone” in Los Angeles — while two-timing him in New York with married actor Macaulay Culkin.

The 18-year-old actress’ wild fling shattered the romance with her director-boyfriend Morgan J. Freeman — leaving him brokenhearted.

After Morgan learned about Mila and Macaulay rendez-swooning in the Big Apple, a pal disclosed: “He feels betrayed. She knew what this would do to him. It just killed him.”

Mila, who plays perky high-schooler Jackie on the FOX sitcom, had been dating the filmmaker since last June. He directed her in the soon-to-be-released thriller “American Psycho II.”

But in May, she dumped Morgan, 32, after meeting 21-year-old Macaulay, who’s separated from his own spouse.

“It was like a knife through Morgan’s heart. She didn’t take his calls for days while she was in New York, and the next thing he discovers, she’s having a hot romance with Macaulay,” an insider told The ENQUIRER.

“In New York, Mila and Macaulay were seen holding hands and gazing into each other’s eyes in Don Hills’ nightclub. And they were wrapped around each other like snakes as they left the trendy Spa club the next night.

“Before Mila had left for her trip to New York, she and Morgan had been having a lot of trouble because of their age difference. Morgan was ready to get married, but Mila wanted to rock ‘n’ roll with her teen pals.

“When Mila didn’t get her way, she would scream and rant and carry on, accusing Morgan of making her miserable and never doing the things she wanted to do with her friends.”

Mila’s shouting was so loud it sometimes disturbed neighbors near Morgan’s Los Angeles home.

“I could hear her screaming, ‘You did this, you did that!'” disclosed a neighbor. “Mila has some lungs on her.”

Just before Mila left for New York, “she and Morgan decided to take a break from each other and figure out whether they had a future together or not,” revealed the insider. “But Morgan never in a million years expected Mila to paint the town red with Macaulay.

“Mila always told Morgan she didn’t want to be seen out in public with him because she didn’t want her private life on the news. But she didn’t seem to have any problem being seen all over New York with Macaulay!”