Jeremy Piven DATING Again — Meet His New Girlfriend!

Jeremy Piven is dating Siobhan Dillon, the actress playing Betty Shaffer on Broadway in the revival of Sunset Boulevard — and RadarOnline.com has all the exclusive details.

"Jeremy was at the premiere last night seemingly by himself," a source told RadarOnline.com. "No one knew why he was at the opening night alone."

"He seemed very out of place but he was attending the show to see his new girlfriend on stage!" the insider then added, revealing the Entourage actor's budding romance.

32-year-old Dillon, an English actress, first shot to fame when she performed in the British talent show-themed television series How Do You Solve a Problem Like Maria? on BBC One in 2006. Since then she's performed in numerous West End productions and recently received her green card in the United States, according to her Instagram account.

"She's a good girl. Let's hope he treats her right," insiders told RadarOnline.com.

It's no secret that Piven's reputation in Hollywood isn't the most favorable. In 2013, a 31-year-old journalist who met Piven in 2008, claimed she spent several nights with the actor, whom she described as arrogant, sarcastic and disparaging.

"He was picked for the Ari Gold role for a reason," Sarah Tressler told Star magazine in the exclusive interview.

Then, during his own Broadway run, Piven quickly pulled out of Speed-the-Plow after insisting he had a serious health scare brought about by eating too much sushi, and left his costar Elizabeth Moss and the rest of the cast hanging.