Hollywood's glitterati are set to gather to celebrate the best performances in film at the annual Academy Awards, a ceremony expected to turn into a toast to blockbuster atomic bomb drama Oppenheimer.
Talk show host Jimmy Kimmel returns for the fourth time to emcee the film industry's highest honours from the Dolby Theatre in Los Angeles.
The live broadcast starts at 4pm local time (2300 GMT), an hour earlier than usual.
Oppenheimer, the three-hour drama directed by Christopher Nolan, leads the field with 13 nominations.
The movie is the frontrunner to win the prestigious best picture prize, capping its sweep of other major awards this year.
"If the best picture isn't Oppenheimer, it will be one of the biggest upsets, if not the biggest upset, in the history of the Oscars," said Scott Feinberg, executive editor for awards at The Hollywood Reporter.
After 2023 was marred by actors' and writers' strikes, the Oscars give Hollywood a chance to celebrate two global hits.
Oppenheimer and feminist doll adventure Barbie, another best picture nominee, brought in a combined $US2.4 billion ($A3.6 billion) in a northern summer box office battle dubbed Barbenheimer.
Oscar producers said they have planned unannounced cameos and other surprises to entertain audiences.
"My biggest hope is that they go through a range of emotions with us, that they feel happiness and joy, that we maybe make them shed a tear," executive producer Raj Kapoor said.
"And then they somehow feel connected and inspired to also live their dreams."
Supporting actor nominee Ryan Gosling will sing the '80s-style rock anthem I'm Just Ken from Barbie.
Members of the Osage Nation will perform the nominated Wahzhazhe (A Song for My People) from Killers of the Flower Moon.
Cillian Murphy, the Irish actor who played physicist J Robert Oppenheimer as he led the race to build the first atomic bomb, is considered the favourite for best actor.
Murphy's main competition, according to awards pundits, is The Holdovers star Paul Giamatti.
Best actress could go to Lily Gladstone of Killers of the Flower Moon, the real-life story about a murder plot to take over lucrative Osage oil rights in 1920s Oklahoma.
If she prevails, Gladstone would be the first Native American actress to win an acting Oscar.
Gladstone's rivals include previous Oscar winner Emma Stone, nominated this year for playing a woman revived from the dead in the dark and wacky comedy Poor Things.
The supporting actor race features Oppenheimer star Robert Downey Jr, who played the scientist's professional nemesis, and Sterling K Brown from American Fiction.
Da'Vine Joy Randolph, praised for her role as a grieving mother in The Holdovers, vies for best supporting actress against Danielle Brooks from The Color Purple and others.
Co-produced by and starring Australian actor Margot Robbie, Barbie - 2023's top film with $US1.4 billion ($A2.1 billion) in global ticket sales - might be shut out of the top awards.
Billie Eilish's Barbie ballad What Was I Made For? is likely to win the original song prize, Feinberg said, and the film could snag the awards for costumes and production design.
For Nolan, the night could bring his first directing Oscar, as well as the award for adapted screenplay.
The director of The Dark Knight trilogy, Inception and other acclaimed films has never had a movie win best picture.
The ceremony could end with "the industry-wide coronation for Christopher Nolan", Feinberg said.
With Oppenheimer, "he has made his best possible argument yet for why he is worthy of this recognition", he said.
