The 31-year-old won Best Supporting Actress for her searing turn as the object of a sadistic plantation owner's affection and revulsion in 12 Years a Slave.
"It doesn't escape me for one moment that so much joy in my life is thanks to so much pain in someone else's," she said onstage. "And so I want to salute the spirit of Patsey" – her character in 12 Years – "for her guidance."
Nyong'o, who received a standing ovation, held back tears as she thanked her director, Steve McQueen, for "putting me in this position – this has been the joy of my life."
"When I look down at this golden statue, may it remind me and every little child that no matter were you're from, your dreams are valid," she said.
12 Years marked the actress's screen debut, gaining her entry into a rarefied circle of thespians who've won an Oscar for their first movie roles.
The Yale School of Drama alum – who was born in Mexico and raised in Kenya – had yet to graduate from her program when she was offered the role of Patsey in 12 Years. She can also be see in the high-altitude thriller Non-Stop.
Other contenders up for the Best Supporting Actress prize included Sally Hawkins in Blue Jasmine, Jennifer Lawrence in American Hustle, Julia Roberts in August: Osage County and June Squibb in Nebraska.
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