Branagh paid tribute to "that amazing city of Belfast on the fabulous island of Ireland".
Kenneth Branagh became the latest Irish person to win an Oscar at the 94th Academy Awards on Sunday (27 March).
His film, Belfast, was nominated in several categories, including Best Picture, Best Supporting Actor, Best Supporting Actress, and Best Original Song.
However, it was in the Best Original Screenplay category that Belfast came out on top, beating out Don't Look Up, Licorice Pizza,
The Worst Person In The World, and King Richard.
The film had also won Best Screenplay at the
Golden Globes earlier this year.
Branagh has set a new record in Oscar history, being nominated eight times in seven different categories throughout his career.
The Best Original Screenplay Oscar is his first win in his career.
"Academy voters, I thank you, my fellow nominees, I salute you," Branagh said in his acceptance speech.
"This is an enormous honour for my family.
"It's a great tribute to an amazing city and fantastic people.
"We lost some people along the way, Johnny Sessions, Jim Dornan, Leah Newman.
"We miss them, we love them, we will never forget them.
"We will never forget those lost in the heartbreaking, heartwarming, human story of that amazing city of Belfast on the fabulous island of Ireland," he concluded.
The last Irish person to win an Oscar was Benjamin Cleary, for his short film
Stutterer, first shown at the Galway Film Fleadh.
Only 13 Irish creatives have won an Oscar since the Awards began in 1929.
Previous winners include Daniel Day Lewis, Brenda Fricker, Neil Jordan, and Martin McDonagh.
CODA took home the award for Best Picture, with Will Smith (King Richard) and Jessica Chastain (The Eyes of Tammy Faye) winning Best Actor and Best Actress respectively.
Smith has been the subject of major controversy following a heated exchange between himself and host Chris Rock, which saw
Smith slapping Rock during the programme.
