Australian actor. He began acting as a teenager and became known for his rugged good looks, charisma, and versatility. His first breakthrough role for international audiences was in the teen comedy 10 Things I Hate About You (1999), a modern remake of Shakespeare's The Taming of the Shrew. He gained international acclaim and an Academy Award nomination for his role as a gay cowboy in the Ang Lee drama Brokeback Mountain (2005).
After his breakthrough he shunned the teen film genre to star in a variety of dramatic films from the late 1990s, including the Australian films Two Hands (1999) and Ned Kelly (2003), and the Hollywood dramas The Patriot (2000), A Knight's Tale (2001), Monster's Ball (2001), The Four Feathers (2002), and I'm Not There (2007). He received the 2009 Academy Award for Best Supporting Actor posthumously for his role as the Joker in the Batman film The Dark Knight (2008). He died during the filming of the fantasy The Imaginarium of Doctor Parnassus (2009), and other actors filled his role for dream sequences.
He was born in Perth and developed an interest in acting while attending the Guilford Grammar School. He performed on stage with the Globe Shakespeare company in Perth, and went on to be cast in the Australian television series Sweat (1996), in which he played a gay cyclist. He was introduced to a US audience in the television series Roar (1997), filmed in Australia, in which he played a Celtic warrior prince, attracting a wide audience of female fans. He also appeared on several other Australian television series, including Ship to Shore, Bush Patrol, and Corrigan. His first film role was in the Australian teen film Blackrock (1997).