Anti-war German drama All Quiet on the Western Front won seven prizes, including best picture.
Irish tragicomedy The Banshees of Inisherin took four trophies, including best British film.
Baz Luhrmann's flamboyant musical biopic Elvis also won four on Sunday night in London, including best costume design for the director's partner Catherine Martin and casting and hair and makeup trophies.
Butler was named best actor for his work on Elvis while the best actress prize went to Blanchett for orchestral drama Tár.
All Quiet filmmaker Edward Berger was named best director.
A visceral depiction of life and death in the World War I trenches, German-language anti-war drama All Quiet on the Western Front had led the pack with 14 nominations.
It received a handful of early awards for best-adapted screenplay, cinematography, sound, score and a film not in English, cementing its favourite status when filmmaker Edward Berger was named best director.
Irish tragicomedy The Banshees of Inisherin and madcap metaverse romp Everything Everywhere All at Once received 10 nominations each, including best picture.
Banshees won the separate award for best British film.
"Best what award?" joked writer-director Martin McDonagh of the film, shot in Ireland with a largely Irish cast and crew.
It has British funding, and McDonagh was born in Britain to Irish parents.
"Banshees" also won for McDonagh's original screenplay, and awards for Kerry Condon as best supporting actress and Barry Keoghan for best supporting actor.
Actor Richard E. Grant hosted the ceremony, walking onstage in a luxurious white cape after a jokey introductory film that saw him taking advice from Steve Martin and pulling up to the concert hall in the Batmobile.
Joking about the infamous altercation between Will Smith and Chris Rock at last year's Oscars, Grant said: "Nobody on my watch gets slapped tonight. Except on the back."
West Side Story star Ariana DeBose opened the show by performing Sisters are Doin' it for Themselves, with an added rap shoutout to some of the nominated women, including Cate Blanchett, Viola Davis and Michelle Yeoh.
Guests and presenters walking the red carpet on the south bank of the River Thames included Colin Farrell, Ana de Armas, Eddie Redmayne, Brian Cox, Florence Pugh, Catherine Zeta-Jones, Cynthia Erivo, Julianne Moore and Lily James.
Many wore blue ribbons in support of refugees and displaced people.
Heir to the throne Prince William, who is president of Britain's film and television academy, was in the audience alongside his wife Kate, Princess of Wales.
