Naomi Watts and Liev Schreiber are ecstatic after the birth of their son, Alexander, in a Los Angeles hospital.
It is the Hollywood couple's first child and a dream come true for Watts.
In recent years the 38-year-old has dropped hints she wanted a child and, after a failed romance with fellow Australian actor Heath Ledger, she fell in love with San Francisco-born Schreiber, a lanky Tony Award-winning actor.
"The parents are ecstatic, and both Mum and baby are doing great," Watts' publicist, Robin Baum, told Reuters.
Watts named her son Alexander Pete Schreiber in honour of her late father, Peter Watts, a former sound engineer for pioneering British band, Pink Floyd, who died when she was seven.
The birth came as a surprise for the couple as it occurred a week ahead of schedule.
Alexander was born at a hospital nearby Watts' home in the exclusive neighbourhood of Brentwood yesterday afternoon.
Alexander weighed 3.2kg according to, Life and Style Weekly, which first broke the news that Watts had given birth. They quoted an insider as saying the couple did not know the sex of their child until he was born.
"This is a dream come true for both of them and they've done everything in their power to make it as special as possible, right down to staying in the dark about the baby's sex right up until Naomi gave birth," the source told the magazine.
The source also said the birth was a surprise.
"Naomi was planning on giving birth next week - her due date was early August - but since she insisted on delivering naturally, she knew there was a chance she would have the baby before the due date. That's what wound up happening," the source said.
Watts, the star of the Peter Jackson-directed King Kong and an Oscar nominee in 2004 for the drama 21 Grams, met Schreiber when the couple made the romantic drama, The Painted Veil, in China in 2005.
Schreiber, 39, was nominated for a Tony Award this year for his Broadway performance in Talk Radio, but missed out.
He won a Tony in 2005 for his performance in Glengarry Glen Ross.
Watts' pregnancy became Hollywood's worst kept secret with the fashion house that dressed her for the Oscars, Escada, sending out a press release declaring she was pregnant.