text: In a 2019 release, MacKay interpreted the role of outlaw Ned Kelly in True History of the Kelly Gang, directed by Justin Kurzel. Adapted from the novel of the same name by Peter Carey, the film premiered at the 2019 Toronto International Film Festival. That same year, MacKay played the lead role of lance corporal William Schofield, a young British World War I soldier in 1917, directed by Sam Mendes. 1917 was nominated for Best Picture in the 92nd Academy Awards, along with nominations in nine other categories, winning three technical awards. MacKay stars in Nathalie Biancheri's film Wolf alongside Lily-Rose Depp, for which principal photography began in Ireland in August 2020. The film premiered at the Toronto International Film Festival in September 2021 as the entry for Ireland, and was theatrically released in December 2021. His acting in Wolf was called by IndieWire as "the best performance of his still-rising career".
  In October 2021, MacKay was cast in a Golden Age musical film The End along with Tilda Swinton and Stephen Graham, directed by Joshua Oppenheimer, and in 2022, he starred in Christian Schwochow's film Munich – The Edge of War for Netflix. In 2023, Mackay starred in LGBT revenge thriller Femme alongside Nathan Stewart-Jarrett, for which he won Best Joint Lead Performance in the British Independent Film Awards. Also in 2023 MacKay starred in the science fiction film The Beast.