Sia has helped write more hit songs with big-name artists than you might imagine. Here are four songs you didn't know Sia wrote.

Sia will release "Everyday is Christmas (Snowman Deluxe Edition)," a new version of her 2017 holiday album.

Sia (born Sia Furler) is one of the most prolific hit songwriters of the past 20 years and is responsible for billions of streams.