Australian Lee Smith has won best film editing for his work on World War II drama Dunkirk.
Earlier, Jordan Peele became the first black screenwriter to win the Best Original Screenplay award for Get Out.
Allison Janney took home the best supporting actress Oscar for her role in I, Tonya, which her Australian co-star - Margot Robbie - is also nominated for in the best actress category.
Sam Rockwell won the Oscar for best supporting actor for his role in Three Billboards Outside Ebbing, Missouri.
The dark comedy is in pole position for the most prestigious prizes, although fairytale romance The Shape of Water leads the overall charge with 13 nominations on a night expected to highlight Tinseltown's campaigns against sexual misconduct and gender inequality.
Meanwhile best documentary feature went to Icarus - which focuses on Russia's Olympics doping scandal.
Hollywood was sprinkled with stardust on Sunday as the movie industry's A-listers came out for the Oscars, hosted by late night funnyman Jimmy Kimmel.
Kimmel targeted disgraced movie mogul Harvey Weinstein following dozens of allegations of sexual misconduct "was long overdue", along with the demise of numerous other Tinseltown figures caught up in the scandal.
"We can't let bad behaviour slide anymore. The world is watching us. We need to set an example," he said.
"And the truth is, if we are successful here, if we can work together to stop sexual harassment in the workplace, if we can do that, women will only have to deal with harassment all the time at every other place they go."
Kimmel highlighted a number of milestones, including the oldest acting nominee, 88-year-old Christopher Plummer (All the Money in the World) and the debut film of Jordan Peele, who was nominated for best directing, producing and writing for his hit racial satire Get Out.
"If you are a nominee tonight who isn't making history, shame on you," he joked.
But the host highlighted the work of the #MeToo and Time's Up campaigns against sexual misconduct and gender inequality, pointing out that only 11 per cent of movies are made by women.
"We will always remember this year as the year men screwed up so badly, women started dating fish," he joked, in a reference to the plot of Guillermo del Toro's The Shape of Water.
Hollywood is set for a real-life cliffhanger Sunday at the Oscars - the race for best picture is coming down to the Three Billboards has begun to pull away in late betting for the industry's biggest prize, but Oscarologists believe The Shape of Water and socially-conscious horror movie Get Out will make it a photo finish.
"I don't remember a year with so much uncertainty. There are at least four strong possibilities to win," Variety's awards editor Tim Gray told AFP, adding Christopher Nolan's sweeping war epic Dunkirk to the mix.
"I'm guessing that The Shape of Water will win, but that's just a guess."
The 90th Academy Awards will be beamed live around the world by ABC from Hollywood's Dolby Theatre.
The show caps a difficult few months during which the industry has declared war on the pervasive culture of sexual impropriety unearthed by the downfall of movie mogul and alleged serial sex attacker Mr Weinstein.
With the #MeToo and Time's Up campaigns against sexual misconduct and gender inequality dominating the 2018 awards circuit, this year's Oscars gala is seen as an opportunity for Tinseltown to support female filmmaking.
Winners so far
- Best supporting actor: Sam Rockwell, Three Billboards Outside Ebbing, Missouri
- Makeup and hairstyling: Kazuhiro Tsuji, David Malinowski and Lucy Sibbick, Darkest Hour
- Costume design: Mark Bridges, Phantom Bridges
- Documentary feature: Icarus
- Sound editing: Richard King and Alex Gibson, Dunkirk
- Sound mixing: Gregg Landaker, Gary A. Rizzo and Mark Weingarten, Dunkirk
- Production design: Paul Denham Austerberry (production design), Shane Vieau and Jeffrey A. Melvin (set decoration), The Shape of Water
- Foreign Language Film: A Fantastic Woman
- Supporting Actress: Allison Janney, I, Tonya
- Animated Short: Dear Basketball
- Animated Feature: Coco
- Visual Effects: John Nelson, Gerd Nefzer, Paul Lambert and Richard R. Hoover, Blade Runner 2049
- Film Editing: Lee Smith, Dunkirk
- Documentary Short: Heaven is a Traffic Jam on the 405
- Live Action Short: Chris Overton and Rachel Shenton, The Silent Child
- Adapted Screenplay: James Ivory, Call Me By Your Name
- Original Screenplay: Jordan Peele, Get Out
- Original Score: Alexandre Desplat, The Shape Of Water
- Cinematography: Roger A. Deakins, Blade Runner 2049
- Original Song: Kristen Anderson-Lopez and Robert Lopez, Remeber Me (Coco)
Greta Gerwig is only the fifth woman in Oscars history to be nominated for best director, but faces tough competition from Guillermo Del Toro, the runaway favourite for The Shape of Water.
There was also the first nod in history for a female cinematographer, Rachel Morrison, who shot Dee Rees's racial drama Mudbound.
Avoiding another flub
The Time's Up initiative is not planning a coordinated protest on Sunday - like the striking red carpet "blackout" at the Golden Globes.
But leaders of the movement told journalists there would be "a moment that's been carved out" during the ceremony.
"It's really important that you know that Time's Up is not about the red carpet," powerhouse Hollywood producer Shonda Rhimes said.
"And those women you saw on the red carpet representing Time's Up are now off the red carpet working their butts off being activists."
In another nod to the women's movements, the Academy of Motion Picture Arts and Sciences has tapped past winners Jennifer Lawrence and Jodie Foster to present the best actress Oscar, according to Variety.
Traditionally, the previous year's best actor winner would present that statuette, but Casey Affleck, who triumphed in 2017 for Manchester by the Sea, withdrew under a cloud of sexual harassment accusations he denies.
One political statement on the red carpet may come in bright orange - some A-listers will reportedly wear orange US flag pins in a call for tougher gun control.
Organisers are looking to rebound after last year's flubbed announcement by Warren Beatty and Faye Dunaway of the best picture winner - the trophy was initially given to La La Land when the actual winner was Moonlight.
"In a surprise turn of events, Beatty and Dunaway have been tapped to present the same prize this time around, according to The Hollywood Reporter, although the Academy did not respond to AFP's request for confirmation.
McDormand, Oldman in pole position
The Shape of Water, a Cold War-set story of love between a mute cleaning woman and a mystery merman-like creature, tops the nominations with 13, although observers expect the spoils to be fairly evenly spread.
Dunkirk heads into Sunday's gala in second place with eight nods, while Three Billboards picked up seven.
Frances McDormand (Three Billboards) and British veteran Gary Oldman (Darkest Hour), who have dominated the awards season, are expected to bag the lead acting statuettes.
Disney-Pixar's Coco seems a near-sure bet to pick up the award for best animated film.
And A Fantastic Woman - a love story from Chilean director Sebastian Lelio with a much-praised star turn from transgender actress Daniela Vega - is tipped to win best foreign-language film honours.
The intermittent weekend rain is expected to taper off in time for Sunday's ceremony, but temperatures will be a bit cool as about 3,400 guests descend on Hollywood Boulevard.
