Actress Olivia Wilde is a new mum.

The Tron: Legacy star and fiance Jason Sudeikis have named their firstborn Otis Alexander.

Wilde took to on Wednesday (23Apr14) to announce the happy news, writing, "Ladies and gentlemen, Otis Alexander Sudeikis has Left the building! (I’m the building)."

She also posted a sweet photo of new mum and baby, who arrived 10 days early.

The 30 year old confirmed pregnancy reports in October (13), nine months after she and We're the Millers star Sudeikis became engaged.