Charlize Theron is ''very happy'' with Sean Penn.

The 'A Million Ways to Die in the West' actress, who has an adopted two-year-old son Jackson, started dating the 'Milk' star late last year and is besotted with the Oscar-winning actor.

Asked about their romance, the 38-year-old star told 'Extra': ''I am very happy. I will say that. I'm very happy. I'm not very good at talking about my private life, but we are very happy, yes.''

The couple have been tight-lipped about their relationship since they were first photographed enjoying a New Year's holiday to Hawaii in early January, but have attended a number of red carpet events together.

Sean, 53, was present for the premiere of the blonde beauty's new movie in Los Angeles earlier this week and the duo were spotted looking very cosy at the after party.

An eyewitness told UsMagazine.com: ''They were very touchy feely and sweet. She was caressing his back as they chatted closely.

''They left on the early side. Sean held her hand and walked her to the car.''

A source previously claimed that the couple, who recently moved in together in LA, have also talked about adopting a child together.

Sean already has two children, Dylan, 23, and Hopper, 20, with his ex-wife Robin Wright.