Charlize Theron and Sean Penn attend the Help Haiti Home Gala on January 11, 2014 in Beverly Hills, California.

Charlize Theron and Sean Penn attend the Help Haiti Home Gala on January 11, 2014 in Beverly Hills, California. Photo: Getty

Actress Charlize Theron has fuelled rumours she is preparing to wed boyfriend Sean Penn after she was photographed wearing a new sparkler on her ring finger on Wednesday.

The Oscar winner, who is mum to adopted son Jackson, began dating her longtime friend Penn late last year and recent reports suggest the highly-private couple is planning to take their relationship to the next level by walking down the aisle.

Theron and her new man are set to exchange vows in her native South Africa later this year, according to Us Magazine.

Sean Penn and Charlize Theron attend the Christian Dior show as part of Paris Fashion Week - Haute Couture Fall/Winter 2014-2015 on July 7, 2014 in Paris.

Sean Penn and Charlize Theron attend the Christian Dior show at Paris Fashion Week on July 7, 2014. Photo: Getty

New pictures of the actress arriving at Los Angeles International Airport have given weight to the claims.

In the snaps, the 38-year-old star of George Miller's upcoming Mad Max: Fury Road film, flashes what appears to be a diamond engagement band on her left ring finger.

A representative for Penn has declined to issue a statement on the report, while a spokesperson for Theron has yet to respond to a request for comment.

The actors have been dodging proposal rumours ever since they got together in January, making their first public appearance at Penn's third annual Help Haiti Home gala.

If the rumours are true, it will be Theron's first marriage, while 53-year-old Penn was previously married to Madonna and House of Cards actress Robin Wright.

WENN