Leonardo DiCaprio has won his first Oscar, having been nominated six times.
Accepting his best actor award for The Revenant, DiCaprio said: "Let us not take our planet for granted. I do not take tonight for granted."
Britons Mark Rylance and Sam Smith won for best supporting actor and best original song. Mad Max: Fury Road, nominated for 10 Oscars, has picked up six, including one for Briton Jenny Beavan.
She won the best costume design award for her work on the film. Brie Larson was named best actress for Room.
DiCaprio received a standing ovation as he picked up the award. Alejandro Inarritu also won the best director Oscar for the survival epic.
Inarritu said it was a "great opportunity to our generation to liberate ourselves from all prejudice", saying the colour of someone`s skin should be "as irrelevant as the length of their hair".