Sienna Miller has had a baby girl.

The 30-year-old actress and her fiance Tom Sturridge, 26, welcomed their first child into the world over the weekend in London and the gender of the tot has now been revealed.

A source has confirmed the baby's sex to UsMagazine.com but details about the child's weight and name are still unavailable.

Although news of Sienna's pregnancy broke earlier this year, the 'G.I. Joe: Rise of Cobra' star was very reluctant to talk about it.

The blonde beauty admitted she did not want to share details of the pregnancy because she didn't want anything to jeopardize her attempts to keep her private life out of the public domain.

In March, she said: ''I'm in my second trimester, so I'm I-can-talk-about-it pregnant, even though I'm under strict instructions not to say anything as it would completely defeat the point of everything I've tried to achieve in the last eight years.''

Sienna started dating 'The Boat That Rocked' actor Tom - who is friends with Robert Pattinson - just a few months after she split from fiance Jude Law for a second time in February 2011.