Kate Hudson and Matt Bellamy have become parents to a baby boy.
The couple's first child together, a "healthy baby boy", was born in Los Angeles.
Hollywood star Kate, 32, already has a seven-year-old son, Ryder, with her former husband, Black Crowes lead singer Chris Robinson, who she divorced in 2007.
The actress and her Muse frontman fiance, who got engaged in April, did not know the sex of the child before the birth - but Kate has previously said that she thought she was having a girl.
The film star daughter of actress Goldie Hawn said in a recent interview that she had been doing "the pendulum test" to determine the sex of the child, adding: "It goes in a circle if it's a girl and it usually goes back and forth if it's a boy.
"It's a circle... it's saying it's a girl," she told the Today Show in the US.
She added: "She's so nuts in here. It's got the Hawn gene. It's got my mum's lineage for sure. It's dancing every day."
Kate's publicist Brad Cafarelli told the Associated Press that "Matthew and Kate welcomed a healthy baby boy" in Los Angeles on Saturday.
The actress, whose stepfather is the actor Kurt Russell, has previously said of her British rock star fiance: "He's a beautiful man and I'm excited."
Kate was nominated for an Oscar for 2000's Almost Famous, and is reported to have been offered the role of porn legend Linda Lovelace in a new biopic.