Just hours before her Sydney gigs on Monday, Billie Eilish shot a mystery project in Alexandria with Kiwi DJ Zane Lowe.

A makeup artist accompanied the 20-year-old American actress.

Billie kept her outfit simple, with her go-to ripped baggy pants and a green patterned sweatshirt.

A little pouch bag worn crossbody and a pair of Converse sneakers completed the Bad Guy singer's outfit.

As DJ Zane Lowe, presenter of The Zane Lowe Show, accompanied her; she was then spotted making her way to a black van.

On Tuesday night, Billie will commence the Australian leg of her tour by performing at three concerts at Sydney's Qudos Bank Arena.

From Saturday, she will perform three gigs in Brisbane before travelling to Melbourne, where she will play four shows.

The Happier Than Ever globe tour will end after Billie performs two concerts in Perth.

Grammy Award winner last visited Australia in 2019.