Cillian Murphy has become the first Irish-born winner of the best actor award, as Oppenheimer swept the Oscars.
The film dominated proceedings, winning best picture, best director for Christopher Nolan, and best supporting actor for Robert Downey Jr.
Murphy was named best leading actor for his acclaimed portrayal of theoretical physicist J Robert Oppenheimer.
The actor said he was “overwhelmed” to have won, adding: “I’m a very proud Irishman standing here tonight.”
He thanked Nolan and producer Emma Thomas for “the wildest, most exhilarating, most creatively satisfying journey you’ve taken me on”.
Murphy also paid tribute to “every single crew and cast member, you carried me through”.
He concluded: “We made a film about the man who created the atomic bomb, and for better or for worse, we are all living in Oppenheimer’s world, so I’d like to dedicate this to the peacemakers everywhere.”
The ceremony saw Oppenheimer win seven prizes overall, while Poor Things took four – including best actress for Emma Stone – and The Zone of Interest scored two.
Downey Jr won best supporting actor for his portrayal of US government official Lewis Strauss in Oppenheimer.
Accepting the award, the actor joked: “I’d like to thank my terrible childhood, and the Academy, in that order.
“I needed this job more than it needed me,” he continued. “I stand here before you a better man because of it.”
The star also paid tribute to his wife Susan Downey, who he said had found him as a “a snarling rescue pet”, adding that she “loved me back to life, that’s why I’m here”.
Downey Jr, best known for his run as Marvel’s Iron Man, has enjoyed a hugely successful Hollywood comeback after serious drug addiction issues more than two decades ago, which saw him serve a prison sentence after missing court-ordered drug tests.
He concluded his speech by telling the audience: “What we do is meaningful and what we decide to make is important.”
Host Jimmy Kimmel joked the cast and crew were “getting Oppen-hammered at the bar”, such was the film’s success.
As he accepted his first ever best director Oscar, Nolan said: “Thank you to those who have been there for me, believed in me for my whole career.”
Addressing the Academy, he said: “Movies are just a little bit over 100 years old, we don’t know where this incredible journey is going from here, but to know that you think I’m a meaningful part of it means the world to me.”
A somewhat disorientated-looking Al Pacino appeared to forget to introduce the 10 nominees for best picture, before going straight to announcing Oppenheimer as the winner of the night’s top prize.
Accepting the prize, producer Emma Thomas said: “I think any of us who make movies dream of this moment. But it seemed so unlikely that it would ever actually happen.”
Oppenheimer also won best editing, original score and cinematography. However, it lost several other technical categories, denying it a record-breaking number of wins.
Instead, the unusual steampunk drama Poor Things won best production design, costume design, make-up and hairstyling, as well as best actress for Emma Stone.
The Yorgos Lanthimos film follows an infant whose brain has been implanted into the body of an adult woman, who then goes on an adventure of discovery across the world.
“This is really overwhelming,” Stone said in her speech. “I am so deeply honoured to share this with every cast member, crew member, every person who poured their love, care and brilliance into the making of this film.”
Best actress was the only major category that awards watchers had struggled to call – it had been seen as a dead heat between Stone and Lily Gladstone for Killers of the Flower Moon.
But Martin Scorsese’s drama about a string of Osage murders in the 1920s went home empty handed despite being nominated in 10 categories at the ceremony.
Barbie, the highest-grossing film of 2023, won only one of the eight prizes it was nominated for – best original song for What Was I Made For? by Billie Eilish.
“Thank you so much to the Academy, I was not expecting this, I feel so incredibly lucky and honoured,” Eilish said as she accepted the award with her brother and collaborator Finneas O’Connell.
Da’Vine Joy Randolph won best supporting actress for her portrayal of a school chef who is trying to cope with the death of her son in The Holdovers.
In her acceptance speech, Randolph told the audience: “For so long I have always wanted to be different. And I now I realise I just needed to be myself, and I thank you for seeing me.”
The Zone of Interest won best sound and became the first British film ever to win best international feature. The critically acclaimed Holocaust drama follows a German family who live next to the Auschwitz concentration camp.
In his acceptance speech, director Jonathan Glazer criticised Israel and the ongoing war in Gaza.
Best documentary feature went to 20 Days In Mariupol. Its director Mstyslav Chernov told the audience that he was “honoured” to become the first Ukrainian Oscar winner.
“I’m probably the first director on this stage to say I wish I would never have made this film,” he said, adding: “I wish to be able to exchange this [for] Russia never attacking Ukraine, never occupying our cities.”
Elsewhere, Anatomy of a Fall won best original screenplay. The film’s director and co-writer Justine Triet joked the Oscar would “help me through my mid-life crisis”.
The film follows a woman accused of killing her husband, with the only nearby witness her visually impaired son.
American Fiction was named best adapted screenplay. Its writer Cord Jefferson said: “I’ve been talking a lot about how many people passed on this movie when discussing it, and I’m worried that sounds vindictive, but it’s more a plea to recognise there are many people out there who want the opportunity I was given.”
The writer said he understood Hollywood “is a risk-averse industry”, but said studios should commission more smaller-scale movies. “Instead of making one $200m movie, try making 20 $10m movies,” he said.
Japanese fantasy film The Boy and the Heron was named best animated feature film, holding off competition from Spider-Man: Across the Spider-Verse.
And director Wes Anderson won his first Academy Award in the live action short category for The Wonderful Story Of Henry Sugar, based on the story by Roald Dahl.
For the fourth time, the ceremony was hosted by Jimmy Kimmel. The US chat show host opened with a monologue which reflected on the past 12 months in the film industry.
Recalling the strikes that brought Hollywood to a standstill, Kimmel paid tribute to the efforts made to get a fair deal for actors and writers.
He joked that actors could now stop worrying about “being replaced by AI, and could go back to worrying about being replaced by younger, more attractive people”.
Turning his attention to Barbie stars Margot Robbie and Ryan Gosling, he said: “If neither of you wins an Oscar tonight, I would like to say you won something much better, the genetic lottery.”
Kimmel also suggested the nominated movies “were too long this year”, adding: “When I went to see Killers of the Flower Moon, I had my mail forwarded to the theatre.
“Killers of the Flower Moon is so long,” he continued, “in the time it took you to watch it, you could drive to Oklahoma and solve the murders yourself.”
Towards the end of the ceremony, Kimmel read out an online post from former US President Donald Trump, who had complained about Kimmel’s performance.
Responding to Trump live on air, Kimmel said: “Thank you President Trump, thank you for watching, I’m surprised you’re still up, isn’t it past your jail time?”