Julian Fernando Casablancas (born August 23, 1978) is an American musician. He is the lead vocalist and primary songwriter of the rock band the Strokes, with whom he has released six studio albums since their founding in 1998. Casablancas released a solo studio album, Phrazes for the Young, in 2009, and has released three albums with the experimental rock band the Voidz.

A native New Yorker, he was born to businessman John Casablancas. His mother, Jeanette Christiansen, married a man who introduced him to the music of the band the Doors, introducing him to rock music. He met bassist Nikolai Fraiture at the age of six, and attended a Swiss boarding school where he met guitarist Albert Hammond Jr. He did not complete high school, but received a GED.

After meeting guitarist Nick Valensi and drummer Fab Moretti at Dwight School in Manhattan, New York the group began experimenting with music together. After adding Hammond Jr., the Strokes were formed. Their debut album Is This It was critically acclaimed, and launched Casablancas and the band to rock stardom. Casablancas was the primary songwriter and creative voice behind the band's early albums, including 2003's Room on Fire and 2005's First Impressions of Earth. After a six-year hiatus, the Strokes released Angles in 2011 and Comedown Machine in 2013 with the band taking a more collaborative approach to these projects. Casablancas would not record another record with the band until 2020's Grammy-winning The New Abnormal, the first such nomination or win for the band.

During a five-year hiatus for the band, Casablancas released his debut solo album, Phrazes for the Young. In the same year he founded the independent record label Cult Records, which has represented artists the Growlers, Rey Pila and Karen O.

Since 2013, he has been the frontman of experimental rock band the Voidz. The band has released three studio albums, Tyranny (2014) , Virtue (2018) and Like All Before You (2024). The band represents an ambition of Casablancas to make less commercial music and explore new themes.