Brad Pitt accepts the award for best performance by an actor in a supporting role for "Once Upon a Time in Hollywood". Picture: AP

Brad Pitt dedicated his Academy Awards win to his children.

The 56-year-old actor - who has Maddox, 18, Pax, 16, Zahara, 15, Shiloh, 13, and 11-year-old twins Knox and Vivienne with former spouse Angelina Jolie - picked up the first award of the evening at Los Angeles' Dolby Theatre on Sunday for Actor in a Supporting Role for 'Once Upon a Time in Hollywood' and reflected on the way his own life had lived up to the title of the movie.

He appeared emotional as he said: "I'm not one to look back but this has made me do so, I'm a bit gobsmacked, I think about my folks taking me to my first drive-thru, taking me to see Butch & Sundance, and moving out here, Geena and Ridley giving me my first shot.

"All the wonderful people I've met along the way, to stand here now - 'Once Upon a Time in Hollywood', ain't that the truth.

"This is for my kids, who colour everything I do. I adore you."

Brad – who beat off competition from Tom Hanks ('A Beautiful Day in the Neighborhood'), ‘The Irishman’ stars Al Pacino and Joe Pesci, and Sir Anthony Hopkins (‘The Two Popes’) to take the award - kicked off his speech by referencing former national security adviser John Bolton, who had refused to testify at President Donald Trump's impeachment hearing, despite having suggested he had important information to give.

Joaquin Phoenix, Renee Zellweger, and Brad Pitt pose in the press room at the Oscars. Picture: AP

He said: "Thank you, this is incredible, really incredible.

“Thank you the academy for this honour of honours. they told me only have 45 seconds up here, which is 45 seconds more than the Senate gave John Bolton this week.

"I'm thinking Quentin does a movie about this, where in the end the adults do the right thing."

He then went on to pay tribute to the film's director, Quentin Tarantino, co-star Leonardo DiCaprio and the rest of the cast, and also hailed the work of stunt teams in honour of his character in the film, stuntman Cliff Booth.

He said: "Quentin, [you're] original, and one of a kind.

"I love the ethos you give Cliff Booth, look for the best in people Expect the worst, but look for the best.

Leo, I'll ride on your coat tails any time man, the view is fantastic. The rest of the cast and crew....

"I also wanna say while we're doing all this, we give a little love to our stunt co-ordinators and our stunt crews."