CitizenFour, about the leaking of classified US government documents by former National Security Agency contractor Edward Snowden, won the Best Documentary Feature Oscar on Sunday.
US director Laura Poitras' film about Snowden, who revealed the massive scope of US intelligence surveillance, beat Finding Vivian Maier, Last Days in Vietnam, The Salt of the Earth and Virunga.
"The most important decisions being made affecting all of us are made in secret. We lose our ability to check the powers that control," said Poitras, standing next to journalist Glenn Greenwald,
"Thank you to Edward Snowden for his courage and for the many other whistleblowers, and I share this with other journalists who are exposing truth."
Snowden himself hailed the film's Oscars triumph.
"When Laura Poitras asked me if she could film our encounters, I was extremely reluctant. I'm grateful that I allowed her to persuade me," he said in a statement released via the American Civil Liberties Union.
"The result is a brave and brilliant film that deserves the honor and recognition it has received."
He added: "My hope is that this award will encourage more people to see the film and be inspired by its message that ordinary citizens, working together, can change the world."
