After being nominated five times, DiCaprio takes home his first Oscar - but The Revenant misses out on the best picture gong.
Leonardo DiCaprio has won his first Academy Award, claiming best actor for his performance in the survival epic The Revenant.
The 41-year-old had previously been nominated five times for acting's highest honour, dating back to his 1993 role in What's Eating Gilbert Grape.
But the much-coveted award eluded him until Sunday night's 88th Academy Awards, held at Los Angeles' Dolby Theatre.
DiCaprio is congratulated by his Titanic co-star Kate Winslet
The film's director, Alejandro Inarritu, took home the award for best director, although The Revenant missed out on the gong for best picture, which went to Spotlight, a recreation of the Boston Globe's probe into sex abuse in the Catholic Church.
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DiCaprio, who received a standing ovation, used his acceptance speech to drive home a message about climate change.
"Let us not take this planet for granted. I do not take tonight for granted," he said.
"It is the most urgent threat facing our entire species and we need to work collectively together, and we need to support leaders around the world who do not speak for the big polluters and the big corporations but who speak for all of humanity."
The Revenant had gone into Sunday's ceremony with a leading 12 nominations, and was among four movies believed to have the best chances for best picture after it won Golden Globe and BAFTA trophies.
The Revenant also won Best Cinematography, but Spotlight took the night's top honour in a surprise ending to Hollywood's glittering awards season.
"This film gave a voice to survivors. And this Oscar amplifies that voice, which we hope will become a choir that will resonate all the way to the Vatican," Spotlight's co-producer Michael Sugar told the audience.
"Pope Francis, it's time to protect the children and restore the faith."
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However, it was George Miller's action epic Mad Max: Fury Road that stole the show, winning six Oscars from 10 nominations.
In the best actress category, first-time nominee Brie Larson was triumphant for her portrayal of a woman held captive for years with her son in Room.
Accepting the award, Larson said: "The thing I love about movie making is how many people it takes to make it.
"Thank you to the movie-goers for going to the theatres and seeing our films."
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Among the surprises of the night was Britain's Mark Rylance, who beat presumed favourite and Creed actor Sylvester Stallone to win the Academy Award for best supporting actor for Bridge of Spies.
There was a strong showing from Britons at the awards.
Sam Smith won best original song for Writing's On The Wall, which he composed with fellow Briton Jimmy Napes for the latest James Bond movie Spectre.
Several Hollywood stars including Will Smith and Spike Lee boycotted this year's awards after an all-white acting nominee line-up was announced for the second year running.
Host Chris Rock addressed the issue in his opening monologue, describing the Oscars as the "white people's choice awards".
Several Hollywood stars including Will Smith and Spike Lee boycotted this year's awards after an all-white acting nominee line-up was announced for the second year running.
Host Chris Rock addressed the issue in his opening monologue, describing the Oscars as the "white people's choice awards".
