Los Angeles, California - Oppenheimer swept the board on Sunday at the Oscars, Hollywood's biggest night of the year, with seven awards including best picture and best director, crowning a triumphant year for filmmaker Christopher Nolan.

Nolan's masterful drama about the father of the atomic bomb, half of last summer's massive "Barbenheimer" phenomenon, also bagged acting prizes for lead Cillian Murphy and supporting actor Robert Downey Jr.

Nolan – a British-American filmmaker hailed as a generational talent – said that film as an art form still has room to grow.

"Movies are just a little bit over 100 years old. I mean, imagine being there 100 years into painting or theater," he told the audience at the Dolby Theatre.

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"We don't know where this incredible journey is going from here. But to know that you think that I'm a meaningful part of it means the world to me."

The haul was not quite complete – Oppenheimer was nominated for 13 prizes, but with seven statuettes on the night it is still one of the most awarded films in Oscar history.

Robert Downey Jr. was recognized for his stellar performance as J. Robert Oppenheimer's political nemesis Lewis Strauss.

"I would like to thank my terrible childhood and the Academy, in that order," Downey said after accepting the statuette.

Downey, who had been the butt of a joke by host Jimmy Kimmel about his well-documented drug problems, lavished thanks on his wife Susan for her support.

"She found me a snarling rescue pet and loved me back to life," he said.

Nolan's cerebral take on the man he has called "the most important person who ever lived" also snapped up prizes for editing, cinematography, and best original score.

"We made a film about the man who created the atomic bomb. And for better or for worse, we're all living in Oppenheimer's world so I would really like to dedicate this to the peacemakers, everywhere," Murphy said as he accepted his award.

The other huge smash of 2023, Greta Gerwig's pop feminist blockbuster Barbie, featured heavily throughout the gala in Los Angeles.

While the movie, which grossed $1.4 billion at the box office, only won one Oscar for best original song, the bubblegum fun it generated provided fodder for the whole evening.

Supporting actor nominee Ryan Gosling brought the house down with a star-studded rendition of I'm Just Ken, accompanied by Guns 'n Roses guitarist Slash, as well as some of his on-screen Ken pals like Simu Liu and Ncuti Gatwa.

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The performance slid into a karaoke session as Gosling passed the microphone around to some of the A-list guests.

Billie Eilish's What Was I Made For? was the winning song from the summer hit film.

The 22-year-old, who delivered a heartfelt rendition of the reflective song, now has two Oscars to her name after a previous win two years ago for James Bond theme No Time To Die with her brother and frequent collaborator Finneas O'Connell.

In one of the few competitive awards of the evening, Emma Stone won best actress for her daring performance in the surreal, Frankenstein-esque Poor Things, which won three other technical prizes.

She pipped Lily Gladstone, who was bidding to become the first Native American to win an acting Oscar for her role in Martin Scorsese's crime saga Killers of the Flower Moon.

Stone, who previously won an Academy Award for La La Land, paid tribute to the other women in her category, and the five women on stage who presented the category.

Stone also beat out Sandra Hueller of Oscars sleeper Anatomy of a Fall.

But the French courtroom thriller did not go home empty handed, with a win for best original screenplay.

Co-writer Justine Triet revealed backstage that the 50 Cent song that features heavily in the film was originally going to be a Dolly Parton track.

"But they refused to give us the rights," she told reporters.

As well as the legacy of Oppenheimer, there were several other reminders of the toll of human conflict.

The United Kingdom scored its first-ever best international film Oscar with Auschwitz drama The Zone of Interest, which also won best sound.

Several nominees wore lapel pins calling for a ceasefire in Israel's assault on the Gaza Strip, while protests erupted around the event's security perimeter.

There were also references to the war in Ukraine, with a best documentary statuette for 20 Days in Mariupol, and a brief tribute paid to Russian opposition figure Alexei Navalny, the subject of last year's Oscar-winning documentary.