Joaquin Phoenix won his very first Oscar on Sunday night for Best Actor for his portrayal of "Arthur Fleck" in Joker. In an emotional speech when accepting his award, the actor mentioned his late brother River, who tragically died from an overdose in 1993.

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Joaquin Phoenix: "Run to the rescue with love and peace will follow."

"I've been a scoundrel all my life. I've been selfish. I've been cruel at times, hard to work with, and I'm grateful that so many of you in this room have given me a second chance," he told the audience.

Phoenix also touched on some "distressing" issues that the world is facing and asked for unity while urging everyone to live with love and compassion.

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To drive his point home, he then quoted a song lyric by River Phoenix while starting to cry. "When he was when he was 17, my brother wrote this lyric," he went on. "He said, 'Run to the rescue with love and peace will follow.'"

Joaquin Phoenix Oscar speech: Watch it right here!

In his category, Phoenix was nominated alongside fellow actors Antonio Banderas (Pain and Glory), Adam Driver (Marriage Story), Jonathan Pryce (The Two Popes) and Leonardo DiCaprio (Once Upon a Time… in Hollywood).