Cox portrayed Owen Sleater in the second and third seasons ofHBO'sBoardwalk Empire (2011–2012) and Jonathan Hellyer Jones in the 2014 filmThe Theory of Everything. More recently, he starred in theRTÉ drama seriesKin (2021–2023) and theNetflixspy miniseriesTreason (2022). Cox's breakout role was as Tristan Thorn in the 2007 fantasy filmStardust, one of a series of roles he had in predominantly British productions during the first decade of his career. He made hisWest End debut the following year in a revival of theHarold Pinter playsThe Lover andThe Collection. Following his successes on-screen in the 2010s, he acted in a 2019 stage production of Harold Pinter'sBetrayal, first in the West End and then onBroadway. He would later make his video game debut in 2025 as Gustave inClair Obscur: Expedition 33.
Cox was born in London, England, and raised inEast Sussex. He is the son of Patricia (née Harley) and Andrew Frederick Seaforth Cox, a publisher.[3][4] He is the youngest of five children and has one brother and three half-siblings from his father's first marriage.[5]
Cox was cast in his first professional role at age eighteen in the psychological thrillerDot the i, released in 2003. Following filming, he enrolled at theBristol Old Vic Theatre School. In the summer following his first year of study, He was cast as Lorenzo in the 2004Al Pacino-vehicleThe Merchant of Venice, breaking the school's policy of not allowing students to audition for outside productions.[10] Subsequently, he decided not to return to school and continued working, appearing in guest spots on TV and supporting roles in movies like the 2005 historical dramaCasanova and the 2006BBC sci-fi filmA for Andromeda.[11]
Cox's breakout role was as the main protagonist, Tristan Thorn, in the 2007 fantasy filmStardust, in which he starred oppositeClaire Danes. The film was successful with both critics and audiences globally and introduced Cox to a wider audience.[12][13] He made his West End debut the following year inHarold Pinter'sThe Lover/The Collection at theAmbassadors Theatre in London. It began previews on 15 January 2008 and opened on 29 January.[14]
Also in 2011, he signed on for a recurring role in the second season of theMartin Scorsese-producedHBOoriginal seriesBoardwalk Empire as Owen Sleater, an Irish enforcer with ties to theIRA.[15][16] His character became a regular for the series' third season, broadcast in September 2012. He received aScreen Actors Guild Award as part of the ensemble in 2011 and another nomination the following year.
In 2013 he starred in the independent filmHello Carter and the BBC Cold War thrillerLegacy. He had lead roles in two unproducedCBS TV pilots: a political drama titledThe Ordained in February 2013 and an untitled Wall Street show executive-produced byJohn Cusack in February 2014.[17][18] At the end of 2013, production began on the filmThe Theory of Everything, where Cox portrays Jonathan Hellyer Jones, the second husband ofJane Hawking. The film premiered at theToronto International Film Festival in September 2014 and was nominated forBest Picture at the2015 Academy Awards.
It was announced that Cox had won the role in May 2014, and later reported that Marvel had considered him for it since 2012.[21][22] Production on the first season began in summer 2014, and it premiered on Netflix in April 2015. It ran for three seasons and was produced over four years, concluding in late 2018. In the following years, Cox shared his interest in reprising the role in a future project,[23] also noting his contractual obligations byMarvel Studios to do so.[24]
AfterDaredevil abruptly ended, Cox took the opportunity to star oppositeTom Hiddleston andZawe Ashton in theWest End production ofHarold Pinter'sBetrayal, which opened on 14 March 2019 and closed on 8 June.[29][30] Cox was sought for the role by directorJamie Lloyd, who had previously directed him in the 2008 production of the Pinter playThe Lover and The Collection.Betrayal transferred to Broadway with the original cast for a 17-week limited engagement, beginning previews on 14 August and closing on 8 December 2019.[31]
During this period, Cox also took part in some of his friends' projects; in late 2018 he acted in the short filmThe Knot, directed byDaredevil andThe Defenders script supervisor Rebecca Schwab,[32] and in a 2019 episode ofDaredevil costarDeborah Ann Woll'sDungeons & Dragons internet showRelics and Rarities.[33]
In fall 2020, Cox began filming theRTÉ Dublin crime seriesKin, in which he stars withAidan Gillen,Clare Dunne,Maria Doyle Kennedy,Ciarán Hinds, andEmmett Scanlan.[34] The eight-part series was released on 9 September 2021, onAMC+ in the US and Canada, and on 12 September 2021, on RTE in Ireland.[35] The show's second season was broadcast in 2023.
In December 2021,Marvel Studios presidentKevin Feige confirmed that Cox would be reprising the role of Daredevil in the studio'sMarvel Cinematic Universe (MCU) productions; his first project "remain[ed] to be seen" at that time.[36] The first Marvel Studios production he appeared in wasSpider-Man: No Way Home (2021),[37] in which Matt Murdock gives legal advice toPeter Parker for ostensibly murderingMysterio. In July 2022, he was confirmed to be reprising the role in theDisney+ television seriesShe-Hulk: Attorney at Law (2022) andEcho (2024).[38] In 2025, he starred in his ownrevival seriesDaredevil: Born Again (2025–present) and additionally lent his voice to the character in the animated seriesYour Friendly Neighborhood Spider-Man.[39] In August 2024, Feige confirmedDaredevil: Born Again was renewed for a second season, with Cox confirming filming will start by March 2025. Filming wrapped in July of that same year.[40][41]
In September 2018, Cox married television producer Samantha Thomas, with whom he has a daughter and a son.[45][46][47][48] At the time of their marriage, they both worked forMarvel Television, where Thomas was Vice President of Original Programming and Cox starred inDaredevil.[46][49] Subsequently, Thomas was the Executive Vice President ofBRON Studios's television division; during her tenure, she and Cox collaborated on the crime drama seriesKin.[50][51][52] The family lives inConnecticut.[53] Cox has previously lived in New York City, Los Angeles, and in theChelsea andHighbury neighbourhoods of London.[54][55] In January 2025, Cox became anAmerican citizen through naturalisation, making him a dual citizen of the UK and US.[52]