Maggie Siff is a first time mum

Sons of Anarchy star Maggie Siff has a new bundle of joy after giving birth to a baby girl named Lucy.

US actress Maggie Siff is a first-time mum after giving birth to a baby girl named Lucy. (AAP)

Former Mad Men and Sons of Anarchy star Maggie Siff is a first-time mum.

The actress and her husband recently welcomed a new member into their family, a daughter called Lucy, and she introduced the tot to fans in a Twitter post on Monday.

Siff shared a photo of herself holding her sleeping baby in her arms, along with the simple caption, "#Lucy".