Joaquin Phoenix won the Academy Award for best actor in a leading role for his performance in "Joker" at the 2020 Oscars Sunday.
The actor, 45, beat out fellow nominees Antonio Banderas ("Pain and Glory"), Leonardo DiCaprio ("Once Upon a Time ... in Hollywood"), Adam Driver ("Marriage Story") and Jonathan Pryce ("The Two Popes").
This is Phoenix's first Oscar win. He's been nominated before, for his performance in "Gladiator" in 2001, "Walk the Line" in 2006 and "The Master" in 2013.
The actor expressed his gratitude to the Academy and his fellow nominees in his acceptance speech.
"I do not feel elevated above any of my fellow nominees or anyone in this room because we share the same love -- the love of film and this form of expression has given me the most extraordinary life," he said. "I don't know what I'd be without it."
He then talked about how acting has allowed him to champion causes and speak up for others.
"I think the greatest gift that it has given me, and many of us in this room, is the opportunity to use our voice for the voiceless," he said. "I've been thinking a lot about some of the distressing issues that we are facing collectively, and I think at times we feel, or are made to feel, that we champion different cause. But for me, I see commonality."
He went on, "I think that whether we're talking about gender inequality or racism or queer rights or indigenous rights or animal rights, we're talking about the fight against injustice -- we're talking about the fight against the belief that one nation, one race, one gender or one species has the right to dominate, control and use and exploit another with impunity."
"I think that we've become very disconnected from the natural world...what we're guilty of is an egocentric world view -- the belief that we're the center of the universe," he said. "We go into the natural world, and we plunder it for its resources. We feel entitled to artificially inseminate a cow, and when she gives birth we steal her baby. Even though her cries of anguish are unmistakable. And then we take her milk that's intended for her calf and we put it in our coffee and our cereal."
He said that he believes sometimes people "fear the idea of personal change because we think that we have to sacrifice something to give something up."
"But human beings, at our best, are so inventive and creative and ingenious, and I think that when we use love and compassion as our guiding principles. We can create, develop and implement systems of change that are beneficial to all sentient beings and to the environment."
He acknowledged that he is not a perfect human being and that many in the room have given him a second chance.
"When we're at our best, when we support each other, not when we cancel each other out for past mistakes, but when we help each other to grow, when we educate each other, when we guide each other toward redemption," he said.
He also mentioned his late brother River Phoenix: "I want to...when he was 17, my brother wrote this lyric, he said, 'Run to the rescue with love and peace will follow.' Thank you."
Phoenix's portrayal of Arthur Fleck in "Joker" marks the second time in Oscar history that an actor has won an Academy Award for playing the same character.
Heath Ledger won a posthumous Oscar for best supporting actor for his performance playing the Joker in "The Dark Knight" in 2009.
The first actors that accomplished this feat were Marlon Brando and Robert De Niro for their portrayals of Vito Corleone in "The Godfather" and the film's second installment, "The Godfather Part II."
Phoenix uses his acceptance speeches to champion causes
Phoenix's best actor Oscar win marks the culmination of his successful awards season run.
He's taken home the award for best actor in a motion picture drama at the Golden Globes, lead actor at the BAFTAs, outstanding performance by a male actor in a leading role at the SAG Awards and best actor at the Critics' Choice Awards among many other accolades.
During past acceptance speeches for the various awards he's received, the actor has used his platform to call out issues he is passionate about, like the lack of diversity in Hollywood and environmental advocacy.
In an impassioned speech while accepting his BAFTA award earlier this month, Phoenix called out "systemic racism" in the film industry. That award show notably drew criticism for its all-white list of nominees in all four leading categories.
"I think that we send a very clear message to people of color that you are not welcome here," he said. "I think that is the message that we are sending to people that have contributed so much to our medium and our industry -- and in ways that we benefit from."
He also acknowledged his own shortcomings, adding that he is "ashamed to say that I am part of the problem."
"This is not a self-righteous condemnation ... I have not done everything in my power to ensure that the sets I work on are inclusive," he shared. "But I think that it's more than just having sets that are multicultural."
"I think that we have to really do the hard work to truly understand systemic racism," he noted. "I think that it is the obligation of the people that have created and perpetuate and benefit from a system of oppression to be the one to dismantle it. So that’s on us."
During his speech at the Globes, Phoenix thanked the HFPA "for recognizing and acknowledging the link between animal agriculture and climate change" with its plant-based menu at the show. He also commended the Critics’ Choice Awards for having a plant-based menu.
"It’s great to vote, but sometimes we have to take on that responsibility on ourselves and make changes and sacrifices in our own lives and I hope that we can do that," he added. "We don’t have to take private jets to Palm Springs for the awards, sometimes, or back."