Madden was born on 18 June 1986 in Elderslie, Renfrewshire, outside the city of Glasgow, where he was also raised alongside his two sisters. His mother, Pat, is a primary school teacher, and his father, Richard, worked as a firefighter. At age 11, Madden joined PACE Youth Theatre to help overcome his shyness. He was soon cast in his first role as young Andy in the film adaptation of Iain Banks’ Complicity, which was released in 2000. He was then cast in the lead role of Sebastian in the children’s television series Barmy Aunt Boomerang, which aired from 1999 until 2000. Madden later stated that he experienced bullying following his performance in Complicity, especially in high school.

He later attended the Royal Conservatoire of Scotland, formerly the Royal Scottish Academy of Music and Drama, in Glasgow, graduating in 2007. He worked with The Arches and the Glasgow Repertory Company during his studies; he also performed in Franz Xaver Kroetz’s play Tom Fool at the Citizens Theatre. After receiving positive reviews, the Tom Fool production transferred to London, where Madden was spotted by a team from Shakespeare’s Globe. In his final year at the conservatoire, he was cast as Romeo in a production of Romeo and Juliet at the modern Globe Theatre in London, after which the company embarked on a tour of the production during the summer of 2007. In her review of the production, Susan Elkin of The Stage highlighted Madden’s “gravelly Glaswegian, almost childlike Romeo”.

He played Callum McGregor in the Royal Shakespeare Company’s production of Malorie Blackman’s Noughts & Crosses in 2008. He then starred as Mark McNulty in the National Theatre of Scotland’s production of Be Near Me in 2009, during which Warwick Thompson of Bloomberg noted Madden’s performance to be “especially good”. Susan Mansfield of The Scotsman stated that Madden had caught critics’ attention, reporting additional positive reviews of his work by The Daily Telegraph and The Observer. He later gained the lead role of Dean McKenzie in the 2009 BBC comedy-drama series Hope Springs, followed by his roles as Ripley in the 2010 film Chatroom, and as Theatre of Hate singer Kirk Brandon in the 2010 film Worried About the Boy.

Madden won Most Stylish Male at the Scottish Style Awards in October 2009 and was also named in Esquire’s Hottest Stars for 2010. He was named one of Screen International’s Stars of Tomorrow in 2011. In 2019, Madden was recognised with the GQ Men of the Year Award for Hugo Boss Most Stylish Man. He was also named one of the 100 most influential people in the world by Time magazine in the same year.

Madden starred as Robb Stark in the HBO series Game of Thrones, based upon the series of novels titled A Song of Ice and Fire by George R. R. Martin, from 2011 to 2013. Madden’s performance in the series propelled him to prominence. During this period, Madden also starred in the Channel 4 comedy-drama series Sirens and in the BBC drama series Birdsong. Madden first obtained his Screen Actors Guild (SAG) card for the 2014 miniseries Klondike, in which he played Bill Haskell, a real-life adventurer who participated in the Klondike Gold Rush. He then portrayed the prince in the live action Disney film Cinderella, which was released in March 2015. The film became a commercial and critical success, receiving positive reviews and grossing over $542 million.

Between 12 May and 13 August 2016, Madden appeared on stage in London’s West End playing the part of Romeo in Romeo and Juliet, where he was reunited with his Cinderella co-star Lily James, who played Juliet, and director Kenneth Branagh. Madden was replaced as Romeo in July 2016 after suffering an ankle injury. He then played the leading role of Cosimo de’ Medici, the son of the founder of the Medici Bank during the Italian Renaissance, in the first season of the Italian-British television drama series, Medici, subtitled Masters of Florence. In the same year, he portrayed American pickpocket Michael Mason in the 2016 action film Bastille Day, starring alongside Idris Elba. He next starred as a DJ in the Netflix romantic comedy film Ibiza alongside Gillian Jacobs, Vanessa Bayer and Phoebe Robinson.

In 2018, Madden garnered acclaim and recognition for his portrayal of Sergeant David Budd, a war veteran and Principal Protection Officer, in the BBC thriller series Bodyguard. Tim Goodman of The Hollywood Reporter wrote that Madden portrayed Budd “with aplomb”, while The Atlantic’s Sophie Gilbert highlighted his “success at conveying [Budd’s] superb instincts, his cool head under fire, and his complex psyche”. The series went on to become the UK’s most watched television drama since current records began, which led to its release to a worldwide audience on Netflix in October 2018. Madden’s performance earned him a Golden Globe Award for Best Actor – Television Series Drama. Bodyguard received a Primetime Emmy Award nomination for Outstanding Drama Series; however, critics and viewers alike expressed disappointment over the fact that Madden did not receive an Emmy nomination for his performance, deeming it a snub.

In 2019, Madden portrayed music manager John Reid in the Elton John biopic Rocketman, which was released in May, and appeared as a lieutenant in Sam Mendes’ war film 1917, which was released in December. He will star as Ikaris in the Marvel Cinematic Universe film Eternals, directed by Chloé Zhao, which is scheduled for a November 2021 release. He has also been cast in a leading role in an upcoming Amazon Studios “multi-series” titled Citadel, executively produced by Anthony and Joe Russo, alongside Priyanka Chopra.

Madden was previously in a relationship with English actress Jenna Coleman. As of May 2019, Madden splits his time between his residence in London and Los Angeles. When asked about his personal life during a New York Times interview following speculation about his relationships and sexuality, Madden stated: “I just keep my personal life personal.” In July 2019, he received an Honorary Doctorate of Drama from his alma mater, the Royal Conservatoire of Scotland.