The former S Club 7 singer, who did not know the sex of the child while she was pregnant, had baby Amelie.
It is the first child for the 32-year-old former Strictly Come Dancing star and husband Alex Bourne.
Her spokesman said: “Rachel Stevens and Alex Bourne are delighted to announce the birth of their daughter Amelie.”
Rachel, who previously dated actor Jeremy Edwards, was the runner-up in Strictly Come Dancing in 2008 and married Alex, 32, who works in property, in London last year.
The star, who has been voted one of the sexiest women in the world by FHM magazine readers, said before the birth: “Neither of us mind what we have but most people think that I’m having a girl, but I really don’t know.”
She added: “I think having children is the most amazing thing. I don’t think I can tell what kind of mum I’d be until I go through it. It’s such a life-changing thing.”