Despite the length and breadth of her career, Allison Janney’s Sunday night Oscar win marked both her first Oscar win and her first Oscar nomination.

The 58-year-old actress cleaned up during awards season, netting a Golden Globe, BAFTA, and SAG Award for her performance in Margot Robbie-led Tonya Harding biopic I, Tonya. Janney's deadpan version of Tonya's mother, LaVona Harding, drew accolades from fans and critics alike.

Janney walked the red carpet on Sunday evening in a Morticia Addams-esque mermaid-cut scarlet Reem Acra gown with floor-grazing sleeves and a plunging neckline.

Allison Janney embed 
Credit: Jeff Kravitz/FilmMagic

The West Wing alum bested fellow nominees Laurie Metcalf, Mary J. Blige, Lesley Manville, and Octavia Spencer, humbly accepting the Oscar for Best Supporting Actress during her speech, which was eloquent, funny, and succinct.

“I did it all by myself,” Janney jokingly began.

“Nothing further from the truth,” she continued. “Thank you to the Academy. My fellow nominees, you represent everything that is good and right and human about this profession. You are all extraordinary.”

“To my I, Tonya family,” she went on, “the magnificent Margot Robbie, the fearless Craig Gillespie, the cast and crew, and bird [her character's pet in the movie], that elevated my work.”

“This is for Hal [her late younger brother, who passed away in 2011 at the age of 49],” she concluded. “I love you very much.”

Later that evening in the press room, Janney took time to reflect on what the Oscar meant to her.

"I kind of didn't dare to dream of things like this, because I didn't want to be disappointed," she admitted. "And I think at a certain point, I had given up thinking this would happen for me because I just wasn't getting the kind of roles in film that would give me attention like this, and that's what my very good friend Steven Rogers did for me. He says he did it—wrote this for me to do just that, to show a different side of me and show that I could—what I could do, and I will never be able to repay him. It's an extraordinary gift he gave me."

After her win, Janney's Mom co-star and close friend Anna Faris gave her a shout out on Twitter, and Janney sent the love right back in the Oscars press room.

"I'm going to have a big crash down after this," Janney said. "So I'm happy that I have Mom—the people at Mom to lift me up and keep me—keep me going and keep me focused. And I'm just happy to have a job to go to tomorrow. But this is extraordinary. Thank you."

Congratulations, Allison!

—With reporting by Brandi Fowler