Just six weeks after his wife filed for divorce, Oscar winning actor and movie director Mel Gibson has announced his Russian girlfriend, Oksana Grigorieva, is pregnant.

Alan Nierob, Gibson’s publicist, said the US-born, Australian-raised actor confirmed during Monday’s taping of that 39-year-old Grigorieva is pregnant.

Citing irreconcilable differences, Gibson’s wife of 28 years Robyn, a former Adelaide dental nurse, filed for divorce on April 13.

Fifty-three-year-old Gibson has seven children with Robyn, but the couple has been separated for almost three years. With no pre-nuptial agreement, she is expected to get half of the reported $US900 million family fortune.

When Leno asked whether he and Grigoreiva planned to marry, the Oscar winner replied, “why would you get married twice?”.

Grigorieva, a singer signed to Gibson’s record label, is reportedly in her second trimester. She has a 12-year-old son with former James Bond leading man, Timothy Dalton.

Gibson is perhaps best know for his leading roles in action movies such as the Mad Max and Lethal Weapon series, as well as his role in Gallipoli .

In 1985, Gibson was the first person to be named by People magazine as The Sexiest Man Alive.

In 1995, Gibson’s direction of Braveheart made him only the sixth actor-turned-filmmaker to receive an Academy Award for Best Director.