She claimed the Oscar for best supporting actress Sunday night for her performance in "Minari" as a grandmother who moves from South Korea to live with her daughter's farming family in Arkansas.
It was the first Oscar nomination in a career that spans five decades for Youn, long a star in South Korea.
She seemed starstruck herself by Brad Pitt, who presented the award -- albeit after mispronouncing her name in the announcement.
"Mr. Brad Pitt, finally, nice to meet you!" she said. "Where were you when we were filming in Tulsa?" Pitt's production company, Plan B Entertainment, was behind "Minari," which was shot on location in Oklahoma. "It's an honor to meet you," she said.
Youn said many throughout the world have badly botched the pronunciation of her name, but "tonight you are all forgiven."
She said she was accustomed to watching the Oscars ceremony on television only, and expressed disbelief at being onstage accepting an Academy Award
"I cannot believe I'm here," she continued, saying she became family with the rest of the "Minari" cast and thanking director Isaac Chung Lee as their "captain."
Red carpet interview: 'Youn Yuh-jung says she feels like she's already won just by being nominated
Last year the South Korean film "Parasite" won best picture and best director, but none of its actors were nominated for Oscars.
"I'd like to thank my two boys who made me go out and work," Youn said while holding her statuette. "This is the result because Mommy worked so hard."
She beat out fellow nominees Olivia Colman, Amanda Seyfried and Maria Bakalova and Glenn Close, who has now been nominated for eight Oscars without a win.
Youn had already won a BAFTA and a Spirit Award for best supporting female actor.
"Never in my dreams did I ever think a Korean actress would be nominated for an Oscar, and I can't believe it's me!" she said. "I am incredibly humbled by the honor. Thank you so much AMPAS, A24, Plan B, my Minari family and our entire cast and crew. We made this film with love, and I thank you for loving us back. And thank you, Isaac. This is all because of you!"
But don't remind Youn that she's been called the Meryl Streep of Korea.
"I know that's a compliment for me but to me, myself, I know myself. I'm just a Korean old lady in Korea. Domestic-wise, I'm well-known in Korea. That's all," she said. "And please, don't compare me with the Meryl Streep. The Meryl Streep. Please don't. She wouldn't like that."
Youn told Deadline that, "It's very stressful. It's not like I'm representing the country by going to the Olympics, but I feel like I'm competing for my country."
What's It About? Minari follows a Korean-American family that moves to an Arkansas farm in search of their own American Dream. The family home changes completely with the arrival of their sly, foul-mouthed, but incredibly loving grandmother.
Oscar Nominations: "Minari" is nominated for six Oscars: Best Picture, Best Director (Lee Isaac Chung); Steven Yeun (Best Actor); Best Supporting Actress (Yuh-Jung Youn); Writing (Best Original Screenplay); Music (Original Score).
"Minari" follows the life of a Korean man who sets out to start a farm in 1980s Arkansas so he can give his family a better life. It's subject matter that the film's writer-director Lee Isaac Chung knows well.
"I took a lot from my own life because I wanted to be as personal as possible with the film," said Chung. "It starts with my memories and a lot of the details of growing up in the South, growing up in Arkansas on a farm."
"Minari" won best foreign language film at the Golden Globes.
Steven Yeun becomes 1st Asian American nominated for best actor for 'Minari'
Included in a year of Oscar firsts is the only Asian American ever to be nominated for best actor.
Steven Yeun, who plays Jacob in the tender family drama "Minari," is the first American of Asian descent to score the award show's top acting nod. He joins nine other actors of color nominated, a record, including fellow best actor nominees Riz Ahmed ("Sound of Metal"), the first person of Pakistani descent nominated in an acting category, and Chadwick Boseman ("Ma Rainey's Black Bottom"), who was nominated posthumously.
"I'm glad for this moment," Yeun said in an interview on the red carpet before the Academy Awards ceremony. "I'm very grateful and thankful that we get a spotlight shown on our film. I hope it finds people -- I hope it finds and connects with them. It's about family and it's about all of us."
Yeun's co-star Yuh-Jung Youn also received a supporting actress nomination, and "Minari" totaled six nods.
Yeun, who is also an executive producer of the film, has been getting all sorts of acting accolades for this performance.
Steven Yeun says 'Minari' is about family, all of us
"I'll be honest. I don't know how to take it. It's an awkward feeling in and of itself," said Yeun.
"Minari" follows a Korean family who moves to a wide-open Arkansas plot to farm the land, a film loosely based on director Lee Isaac Chung's own American immigrant experience.
Yeun too is a child of first-generation immigrants from Korea. The 37-year-old actor was born in Seoul, but his family emigrated when he was 4 and ultimately settled in Michigan.
Yeun told the Associated Press that he brought his father to the film's premiere, and at the end, they stood up, hugged and sobbed.
"This movie is a feeling for me. The feeling is the thing that keeps it connected to everybody," Yeun said. "I don't know how it's getting its way out there, specifically. But I just do know the feeling is getting out there."
Yeun's additional acting credits include "Burning" and "The Walking Dead."
In an interview with Variety before the nominations announcement, Yeun said: "As great as it would be to set a precedent or be part of a moment that breaks through a ceiling, I personally don't want to be ensnared by that moment, either."
The Associated Press contributed to this report.