ASHTON KUTCHER’s irrational jealousy his red-hot girlfriend Mila Kunis is cozying up to Channing Tatum on the set of their new movie, say insiders.

Mila and Channing have hit it off big-time while filming the sci-fi thriller “Jupiter Ascending” in Chicago – and 35-year-old Ashton is acting jealous, say insiders.

In truth, Ashton has NOTHING to worry about, according to a pal who said: “Channing is one of the best flirts in Hollywood, but he’s completely in love with his wife and new baby. So Ashton’s feelings are ridiculous.

“Ashton knows they’re just working together and that his jealousy is irrational, but what gets to him is how Mila raves and raves about how nice and charming Channing is.”

The notion of Channing working with Mila “is burning him up,” the pal added. “He’s even been keeping tabs on her through mutual pals on the movie.”

The “Two and a Half Men” star went so far as to fly to Chicago to check up on Mila, 29, and her 33-year-old co-star.

The actor’s concerns are reportedly getting on the nerves of fiercely independent Mila.

“It’s not hard to imagine why Mila getting so close to Channing would make Ashton worry,” the pal said.

“Who wouldn’t be concerned if their girlfriend was working with the ‘Sexiest Man Alive,’ even if he’s a happily married new father?”