Scarlett Johansson looked breathtaking as she made her first red carpet-appearance since welcoming her son Cosmo on Thursday.

The actress, 36, flashed her cleavage in a glittering top as she attended the American Cinematheque Awards in Los Angeles with her husband Colin Jost, 39.

Scarlett looked picture-perfect as she linked arms with her dapper husband, who was a vision of style in a black tuxedo.

His wife turned every head in a fitted white jacket and matching trousers which cinched into her svelte waist.

It is the first child for the married couple but baby number two for Scarlett, who shares daughter Rose Dorothy, seven, with French journalist ex-husband Romain Dauriac.

SNL funnyman Jost revealed at the time that they had named their baby boy Cosmo, posting onto Instagram: 'Ok ok we had a baby. His name is Cosmo. We love him very much.' He also jokingly wrote that inquiries should be directed to their publicist - tagging his SNL Weekend Update cohost Michael Che.

Colin recently revealed his mother Kerry Kelly was 'slightly thrown' by the name Cosmo and had even asked if it was final.

'My mom, I would say, was slightly thrown by it and didn't quite understand it,' Colin admitted on Late Night with Seth Meyers.

'I don't know if she thought it was kind of, like, a hippie thing... She would call us and say, you know, after three or four days, she'd be like, "Cosmo... And now, is it final? Like, did you submit the birth certificate?" And we're like, "Oh, yeah, we did that at the hospital."