"At 83 years of age, I did not expect to get this award. I really didn't," Anthony Hopkins said of his Oscars win in his Monday morning Instagram video

Anthony Hopkins is expressing his gratitude for taking home the Best Actor honor at the 2021 Oscars ceremony Sunday night.

On Monday morning, the actor posted a video to his official Instagram account, sharing with fans that he was currently "in his homeland in Wales."

"At 83 years of age, I did not expect to get this award. I really didn't. I'm very grateful to the Academy, and thank you," began Hopkins, who won the award for his role as Anthony in The Father.

He went on to honor the late Chadwick Boseman, whom many considered the frontrunner in the category following his Golden Globe and Screen Actor's Guild award wins for best actor in a motion picture, drama, for his role in Ma Rainey's Black Bottom.

"And I want to pay tribute to Chadwick Boseman, who was taken from us far too early," Hopkins said. "And again, thank you all very much. I really did not expect this. So I feel very privileged and honored. Thank you."

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Presenter Joaquin Phoenix, who won the Best Actor category last year for his performance in Joker, accepted the award on Hopkins' behalf, as the celebrated star was asleep in bed at the time and had no idea he'd won what was the final award of the evening or that he had become a record holder as the oldest star to win an Oscar in the category.

"Tony was in Wales, where he grew up, and he was asleep at 4 in the morning when I woke him up to tell him the news," Hopkins' long-time agent Jeremy Barber told PEOPLE.

He added of Hopkins, "He was so happy and so grateful."

"After a year in quarantine, and being double-vaccinated, he was finally able to return to Wales, and age 83, it was a great relief after such a difficult year," Barber continued. "But he loved the role in The Father — it's his proudest performance — and to be the oldest living actor to win in the category means so much to him."

Anthony Hopkins as Anthony in THE FATHER
Anthony Hopkins in The Father
| Credit: Sean Gleason/Courtesy of Sony Pictures Classics

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In The Father, Hopkins plays Anthony, a man with dementia who defiantly rejects caregivers his daughter Anne (Olivia Colman) introduces to him. As his condition worsens, Anthony's confusion surrounding his memories affects his identity and the relationships around him.

Hopkins — who has been nominated six times total at the Academy Awards — also beat out fellow nominees Riz Ahmed (Sound of Metal), Gary Oldman (Mank) and Steven Yeun (Minari) to take home his second Oscar Sunday night.

Listen below to the episode of our daily podcast PEOPLE Every Day for more on the 2021 Oscars. 

He won his first at the 64th Academy Awards, earning the Best Actor trophy for his iconic performance as the expert psychiatrist and cannibalistic serial killer Dr. Hannibal Lecter in the 1992 psychological thriller The Silence of the Lambs opposite Oscar winner Jodie Foster.

The 93rd Academy Awards aired live on Sunday, April 25, at 8 p.m. ET/5 p.m. PT on ABC.