The Oscar-winning actress' fiance, a French actor, confirmed the news to People on Wednesday.
"My son will be an American, but I remain French,” Martinez told the mag while visiting Paris.
Martinez, 47, and Berry, 46, confirmed their baby news in April just as Berry set off to film X-Men: Days of Future Past. They previously would not comment on early reports that they were expecting a boy.
It will be the couple's first child together, though Berry has a young daughter, Nahla, with her ex-boyfriend, model Gabriel Aubrey. Martinez currently lives with Berry in the States.
Martinez spilled the beans during opening night of the Champs-Elysees film festival.