Sia Kate Isobelle Furler ( SEE-ə; born 18 December 1975) is an Australian singer and songwriter. Born and raised in Adelaide, she started her career as a singer in the acid jazz band Crisp in the mid-1990s. When Crisp disbanded in 1997, she released her debut studio album, OnlySee, in Australia. She moved to London and provided vocals for the British duo Zero 7. Sia released her second studio album, Healing Is Difficult, in 2001, and her third, Colour the Small One, in 2004.

Sia moved to New York City in 2005 and toured the United States. Her fourth and fifth studio albums, Some People Have Real Problems and We Are Born, were released in 2008 and 2010 respectively, and both were certified gold by the Australian Recording Industry Association and attracted wider notice than her earlier albums. Uncomfortable with her growing fame, Sia took a hiatus from performing and focused on songwriting for other artists, producing successful collaborations "Titanium" (with David Guetta), "Diamonds" (with Rihanna) and "Wild Ones" (with Flo Rida).

In 2014, Sia broke through as a solo recording artist when her sixth studio album, 1000 Forms of Fear, debuted at No. 1 in the U.S. Billboard 200 and generated the top-ten single "Chandelier" and a trilogy of music videos co-directed by Sia and starring child dancer Maddie Ziegler. Since then, Sia has usually worn a wig that obscures her face to protect her privacy. Her seventh studio album, This Is Acting (2016), spawned her first Billboard Hot 100 number one single, "Cheap Thrills". That year she also began her Nostalgic for the Present Tour, which incorporated dancing by Ziegler and others, and other performance art elements. Her eighth studio album, Everyday Is Christmas, was released in 2017 and reissued in 2018 with three bonus tracks. In 2018, she collaborated with Labrinth and Diplo in the group LSD, and they released their self-titled debut album in April 2019. Sia has written many songs for films, and she directed a feature film, titled Music, which was released in early 2021 alongside an album, Music – Songs from and Inspired by the Motion Picture.

She is an advocate for animal rights. Among the accolades received by Sia are nearly a dozen ARIA Awards, nine Grammy Award nominations and an MTV Video Music Award.