"Lost in Translation" star Scarlett Johansson says she is "not promiscuous" and happy with boyfriend Josh Hartnett.

"Contrary to popular belief, I'm not promiscuous," the 21-year-old actress said in an interview with Allure magazine.

"There does seem to be a mistaken belief out there that I am sexually available somehow -- which is not to say that I'm not open-minded about sex."

In the interview, Scarlett opened up about her relationship with boyfriend and "Black Dahlia" co-star Josh Hartnett.

"Josh is very sweet," said Scarlett. "He's a good boy. A great person. I'm very lucky and I'm very happy."

Johansson also encourages testing for sexually transmitted diseases.

"I get tested for HIV twice a year... One has to be socially aware," she says. "It's part of being a decent human, to be tested for STDs. It's just disgusting behavior when people don't. It's so irresponsible."

Editor: Donald