He had his breakthrough playing the lead role of a closeted sheep farmer in Francis Lee's romantic drama God's Own Country (2017), for which he won a BIFA Award.

He grew up in a Labour-supporting household, but he traces his political awakening to the arts centre's closure when he was eleven, feeling the deep sense of loss in the community.

[2] The production of Bugsy Malone at St Edward's also featured his classmate Tahliah Barnett, who later became a singer under the stage name FKA Twigs.

In 2013, he appeared in Doctor Who as Piotr, in The Magnificent Eleven as Andy, in Law & Order: UK as Rob Fellows, in The Wiper Times as Dodd and in London Irish as James.

"[12] This led to a role as young returning soldier Hugh in Peter Gill's 2014 play Versailles at the Donmar Warehouse in Covent Garden, London.

After a year and a half of auditioning, he landed the role of a Bullingdon toff[clarification needed] named Ed in The Riot Club (2014), Lone Scherfig's adaptation of Laura Wade's play Posh, appearing alongside up-and-coming British actors Sam Claflin, Douglas Booth, Max Irons, Freddie Fox, Ben Schnetzer and Olly Alexander.

[3] In 2015, he played Leo Beresford in Father Brown, a ballroom palace guard in Cinderella and Charlie in the short film Holding on for a Good Time.

He starred opposite his then-girlfriend Hannah Murray in Bridgend, Jeppe Rønde's dark, fictional portrayal of a real town in Wales with an alarmingly high teen suicide rate.

He also played in the Royal Shakespeare Company's production of Thomas Dekker's The Shoemaker's Holiday as Rowland Lacy and Tom Morton-Smith's Oppenheimer as Luis Alvarez at the Swan Theatre in Stratford-upon-Avon.

In 2017, he starred as the young sheep farmer Johnny Saxby in the British drama film God's Own Country directed by Francis Lee.

In preparation for his role, he worked with a Yorkshire farmer, labouring in the fields in between takes to learn the proper techniques and get the right physicality, and eventually birthed over 150 lambs.

[3] In the same year, O'Connor began portraying Charles, Prince of Wales, in Season 3 of the award-winning Netflix historical drama The Crown (2019), starring alongside Olivia Colman, Tobias Menzies and Helena Bonham Carter.

He also played Paul Sheringham in Mothering Sunday, which explores class divides and postwar survivor's guilt in 1924, starring alongside Olivia Colman and Colin Firth.

[23] O'Connor was seen in the drama film Lee, starring Kate Winslet, which is set during World War II and directed by Ellen Kuras.

[26][27] O'Connor will also star opposite Paul Mescal in The History of Sound, a World War I love story film to be directed by Oliver Hermanus.

[30] His performance in the movie "confirmed his place on casting agents' scouting radar as one of those subtle, humble chameleons who can disappear into parts and are dubbed 'actor's actors'.

You isolate yourself from all your friends.The Crown creator Peter Morgan has compared O'Connor to former Barcelona midfielder Andrés Iniesta, a footballer with massive but unobtrusive skill.

[33] In December 2020, he and Emma Corrin offered their company for tea as part of a series of prize draws in support for War Child UK's Torn From Home appeal.