Charlize Theron has been spotted with a ring on her engagement finger – and worried friends now fear for her safety.

They’re warning the actress to think twice about tying the knot with her hot-tempered beau, Sean Penn.

After recently returning from her native South Africa, the 39-year-old beauty was spotted sporting the rock, courtesy of her 53-year-old, Oscar-winning boyfriend.

The two were abroad filming “The Last Face,” which Sean is directing.

But friends are concerned that the fairy-tale romance between the “Monster” actress and the “Milk” star could lead to a nightmare marriage.

In 1987, Sean was sentenced to 60 days in jail for punching a movie extra in the face numerous times on the set of “Colors.”

That same year, he was also charged with domestic assault after he whacked then-wife Madonna across the head with a baseball bat!

The feisty actor was also accused of hog-tying the singer to a chair and leaving her trussed up like a turkey for nine hours!

In 2012, Sean uttered an amazing understatement: “I don’t control my temper well.”

The social activist – who was married to Madonna from 1985 to 1989 and to Robin Wright from 1996 to 2010 – told an interviewer two years ago that many of his relationships were a “fraud” and that he never felt loved.

Yet, while still married to Robin, Sean was reportedly seeing actress Natalie Portman, as well as model Petra Němcová.

Now Charlize’s pals are warning the actress to guard her heart, revealed a source.

“They’re urging her to think twice before finally heading down the aisle with Sean.”