Kate Melina Miller-Heidke (/ˈhaɪdki/; born 16 November 1981) is an Australian singer-songwriter and actress. Although classically trained, she has generally followed a career in alternative pop music. She signed to Sony Australia, Epic in the US and RCA in the UK, but since 2014 has been an independent artist. Four of her solo studio albums have peaked in the top 10 of the ARIA Albums Chart, Curiouser (October 2008), Nightflight (Apri 2012), O Vertigo! (March 2014) and Child in Reverse (October 2020). Her most popular single, "The Last Day on Earth" (July 2009), reached No. 3 on the ARIA Singles Chart after being used in promos for a TV soap, Neighbours, earlier in that year. At the ARIA Music Awards Miller-Heidke has been nominated 17 times.

She represented Australia in the Eurovision Song Contest 2019 in Tel Aviv, Israel with her song, "Zero Gravity" (January 2019). Miller-Heidke is the only person to have sung at Coachella, the New York Metropolitan Opera, and Eurovision. She has won five Helpmann Awards.