Actress Jessica Alba gave birth to her third child, a baby boy, on New Year's Eve.

The Hollywood star and her husband Cash Warren welcomed their newborn son on December 31 and named him Hayes Alba Warren.

The 36-year-old actress took to Instagram to announce the happy news, posting a close-up photo of newborn Hayes along with the caption: "Hayes Alba Warren 12/31/17.

"Best gift to ring in the New Year!!

"Cash and I feel so blessed."

The couple are already parents to nine-year-old daughter Honor and six-year-old daughter Haven.

Alba added that the girls are "already obsessed with their new baby bro".

Alba announced that they were expanding their family in July 2017 by posting a Boomerang which showed her cradling her baby bump along with the caption: "@cash_warren and I are officially going to be outnumbered #babyonboard #herewegoagain #blessed"