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

Wilde announced the happy news on Twitter on Wednesday.

''Ladies and gentlemen, Otis Alexander Sudeikis has LEFT the building! (I'm the building),'' she tweeted, along with a photo of herself and the new bub.

Ladies and gentlemen, Otis Alexander Sudeikis has LEFT the building! (I'm the building) pic.twitter.com/uHfY3adroc — olivia wilde (@oliviawilde) April 23, 2014

She also later joked, on Twitter, that "Having an infant son alerts me to the fact that every man, at one point, has peed on his own face".

Having an infant son alerts me to the fact that every man, at one point, has peed on his own face. #awesome — olivia wilde (@oliviawilde) April 24, 2014

The 30-year-old confirmed pregnancy reports in October, nine months after she and Sudeikis became engaged.

The pair say they have not yet set a date for the wedding.

It will be the second marriage for both.

Sudeikis was previously married to 30 Rock writer Kay Cannon, while Wilde, who eloped at age 18, was married to Italian prince, Tao Ruspoli.

The new parents, who started dating in November 2011, got engaged in January 2013.

WENN and Fairfax Media