LOS ANGELES (Reuters/AFP) - Brie Larson won the Best Actress Oscar on Sunday for her role as a young woman held hostage for years with a young son in the emotional thriller Room.

It is the first Oscar and nomination for the 26-year-old Larson, who has starred in more than 45 films and television shows since beginning her career as a child actress almost 20 years ago.

She beat out previous Oscar winners Cate Blanchett (Carol) and Jennifer Lawrence (Joy), as well as Charlotte Rampling (45 Years) and Saoirse Ronan (Brooklyn) for the accolade.

Larson, accepting the golden statuette, thanked early supporters of the once-obscure film including the Toronto International Film Festival.

"The thing I love about movie making is how many people it takes to make it," Larson said.

"Thank you to the movie-goers. Thank you for going to the theatre and seeing our films."

She was the front-runner for the honour after winning Golden Globe, BAFTA, Spirit and Screen Actors Guild awards.

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