His parents divorced when he was 11 years old, a time during which his interest in acting was beginning to develop. Two years later, he secured a part in children's television series Clowning Around on the ABC.
At the age of 16, Ledger left full time education and played a gay cyclist in the 1996 TV series Sweat before being introduced to American audiences in the Fox series Roar, where he started dating co-star Lisa Zane.
In 1997, he made his film acting debut in the Australian film Blackrock. This was followed shortly after with an appearance in Paws and a few appearances in long-running Aussie soap Home and Away.
He graduated to bigger film roles in 1999, when he played Patrick Verona in 10 Things I Hate About You and had a leading role in Two Hands.
The following year he starred in The Patriot and embarked on a romance with actress Heather Graham, 11 years his senior.
The relationship lasted less than a year, with the couple splitting in June 2001. That year, Ledger starred in international smash-hit A Knight's Tale. Over the next two years, he had mixed success with films, most notably when he played the title role in flop Ned Kelly. It was on the set of Ned, however, that he met Naomi Watts, whom he dated for two years.
In 2004, Ledger signed on to play one of the lead roles in Brokeback Mountain, Ang Lee's award-winning adaptation of a love story about two cowboys. On the set of the film, he met Michelle Williams, with whom he said he fell in love on the first day of filming when he looked after her after she fell during a shoot. The pair moved to a home in Brooklyn and in 2005, Williams gave birth to their daughter Matilda Rose.
Late that year, Brokeback had its greatly anticipated debut. Ledger's performance in the film was likened by Lee to that of "a young Brando" and he was nominated for an Oscar for Best Actor.
At the following year's Academy Awards, he lost out to Philip Seymour Hoffman, who won the Best Actor gong for his role in Capote. Brokeback, having been nominated 8 times, won three Oscars.
In 2007, Ledger and Williams - by this point engaged - surprised fans by announcing that they were splitting up. Ledger started filming for his role as The Joker in The Dark Knight, this year's sequel to Batman Begins.
On January 22, 2008, Ledger was found dead at the age of 28 at an apartment in the SoHo district of lower Manhattan in New York City. He is survived by Matilda Rose, now two years old.