It was the first acting Oscar for Pitt, 56, after three decades in the movie industry. He previously won an Academy Award as a producer in 2014 for best picture "12 Years a Slave."

In "Once Upon a Time," Pitt played the laid-back stunt double and fixit man Cliff Booth to Leonardo DiCaprio's fading TV Western star.

His performance, which has won numerous other accolades, was hailed by critics as the best of Pitt's career and included an extended shirtless scene that sent fans and celebrity media buzzing.

During his speech, he called out the Trump impeachment trial for blocking the testimony of former national security adviser John Bolton.

"They told me I only have 45 seconds up here, which is 45 seconds more than the Senate gave John Bolton this week," he said on stage.

The Academy Award capped a comeback for the actor after a three-year film absence following flops "Allied" in 2016 and "War Machine" in 2017, and an extended period where he was portrayed as the bad guy in divorces from actresses Angelina Jolie and Jennifer Aniston.

Pitt first grabbed audiences' attention with a small part as in 1991's "Thelma & Louise," playing a seductive criminal who conned the character played by Geena Davis.

He went on to lauded performances in films such as "A River Runs Through It" and "Fight Club" and earned Oscar acting nominations for "Twelve Monkeys," "The Curious Case of Benjamin Button" and "Moneyball."

New Zealander Taika Waititi nabbed a best adapted screenplay prize for "Jojo Rabbit," a World War II satire about a young boy living in the waning days of Nazi Germany. Waititi, who is of Maori descent, used his time on stage to dedicate his award to "all the indigenous kids in the world who want to do art and dance and write stories. We are original storytellers and we can make it here as well."

Margot Robbie is Australia's great hope at this year's Academy Awards but Laura Dern is expected to swoop in and take her Oscar.

Dern is the red-hot favourite to win the supporting actress Oscar ahead of Queenslander Robbie.

Australian Associated Press