2002–2012: Beginnings as a child actor In 2002, MacKay was spotted at school by an acting scout who asked him to audition for a role in
P. J. Hogan's 2003 film adaptation of
Peter Pan. He attended a workshop and won the role of one of the
Lost Boys, Curly, in what was his first professional acting job.
2012–2018: Rising popularity In 2012, he played the main character, Private Tommo Peaceful, in
Private Peaceful, and appeared as a paralyzed soldier in the inspirational film
The Best of Men. In 2013, MacKay portrayed Eddie in
How I Live Now opposite
Saoirse Ronan and directed by
Kevin Macdonald, and starred as Davy in the musical film
Sunshine on Leith, featuring songs by
The Proclaimers, directed by
Dexter Fletcher. In 2014, MacKay played the role of Joe, a 20-year-old struggling to
come out in a
homophobic Britain in 1984 in the film
Pride (based on a true story) also starring
Bill Nighy. '' in 2014 In 2015, Mackay took the lead role as Richard Miller in
Eugene O'Neill's coming-of-age play,
Ah, Wilderness! directed by
Natalie Abrahami at
Young Vic. In July 2015, MacKay filled the title role of Lewis Aldridge in the BBC's
two-part television adaptation of
Sadie Jones’ debut novel
The Outcast. In February 2016, he portrayed the part of Bill Turcotte in the Hulu production of
Stephen King's sci-fi/thriller
11.22.63. From 29 March to 14 May 2016, MacKay performed the part of Mick in
Harold Pinter's play
The Caretaker directed by Matthew Warchus at
The Old Vic Theatre in London opposite
Timothy Spall and
Daniel Mays. In the 2016 film
Captain Fantastic, MacKay portrayed Bodevan, eldest son of Ben Cash (
Viggo Mortensen). In 2017, he played Jack, the main character in
Marrowbone, a psychological horror film directed and written by
Sergio G. Sánchez, and also starring
Anya Taylor-Joy,
Charlie Heaton and
Mia Goth. MacKay portrayed
Prince Hamlet in
Ophelia, a 2018 film retelling the story of
Shakespeare's play from the perspective of the young female character
Ophelia. The film premiered at the
2018 Sundance Film Festival, and included
Daisy Ridley,
Naomi Watts,
Clive Owen, and
Tom Felton in the cast. In the 2018 film
Where Hands Touch, MacKay portrayed Lutz, a member of the
Hitler Youth in
Nazi Germany who falls in love with a biracial girl, portrayed by
Amandla Stenberg.
2019–present: 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 the apocalyptic 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. In 2025, MacKay had a starring role in Cornish film
Rose of Nevada which premiered at Venice International Film Festival, and went on general cinema release in Britain and Ireland in April 2026. ==Artistry and media reception==