Gaspard Ulliel's dream had always been to direct a movie, and after completing his studies at the lycée (French high school), he majored in cinema at the University of Saint-Denis, and began his acting career.

He was born in Paris, to Christine, a stylist and runway show producer, and Serge Ulliel, a fashion designer. One of his first professional performances came when he was twelve, in the TV film Une femme en blanc (1997). During the following years, Ulliel continued working on television and was cast in short films such as Alias (1999). He played a young shepherd who was injured by The Beast in Brotherhood of the Wolf (2001), and was then discovered by director Michel Blanc, who offered him a part in Summer Things (2002) which also starred veteran actress Charlotte Rampling. Ulliel then took summer stages at Les Cours Florent and was asked by director André Téchiné to star in Strayed (2003) as Emmanuelle Béart's over. His role as Manech opposite Audrey Tautou in A Very Long Engagement (2004) brought him to stardom. He was nominated thrice for Most Promising Male Newcomer at the César Awards (the equivalent of the Oscars in France) in 2003, 2004 and 2005; he won the last one. Ulliel's lead roles include The Last Day (2004), Jacquou le croquant (2007) and Hannibal Rising (2007), his first major English-language film.

He had a son with his former partner, model and singer Gaëlle Piétri, born in January 2016. They split up in 2020. Gaspard died on 19 January, 2022, in La Tronche, Isère, France, after a skiing accident.