JULIA who?”

Oscar winner Jennifer Lawrence lashed out after Julia Roberts questioned whether the “Hunger Games: Catching Fire” star was fit to take her place as “America’s Sweet­heart.”

Now a bit­ter feud has erupted be­tween the box-office beauties . Sources say Jennifer, 23, brushed off 46-year-old Julia’s remarks as “sour grapes” because the “Pretty Woman” star is over the hill!

Jennifer told a pal, ‘I don’t know what her problem is. I never said a bad word about her in my life,’ ” said a source.

A friend added: “As far as Jen­nifer’s concerned, Julia can keep the damn label of ‘America’s Sweetheart’!

“She’s not interested in it, and she could care less what Julia thinks of her.”

Julia – an Oscar winner for the 2000 drama “Erin Brockovich” – publicly claims to be a fan of Jennifer, who took home an Academy Award for last year’s “Silver Linings Playbook.”

But mother of three Julia got sarcastic when talking about Jen­nifer to an MTV News reporter re­cently. “She shoots flaming arrows,” she said about Jennifer’s role as warrior teen Katniss in the “Hunger Games” blockbusters. “Is this a new cupid tactic?”

Then Julia added: “I think she’s fabulous, but she seems cooler than me. Isn’t she too cool to be America’s Sweetheart?”

The source concluded: “Julia’s just jealous of Jennifer because she’s Hollywood’s new ‘It Girl.’ Jennifer’s attitude is that Julia needs to grow up.”