Hunnam was born in Newcastle upon Tyne, England, the son of William "Billy" Hunnam (1952–2013), a scrap metal merchant, and Jane (née Bell) Hunnam, a business owner. He lived in Australia from the age of 5 to 13 before moving back to the United Kingdom. His maternal grandmother was a portrait artist in Newcastle. Hunnam was the second child, born after brother William "Billy". He has two younger half-brothers, Oliver and Christian, on his mother's side. His parents divorced when he was two years old, and he moved to the village of Melmerby, Cumbria when he was 12, as his mother remarried. He went to Heaton Manor School in Newcastle. After moving, he went to Ullswater Community College then Queen Elizabeth Grammar School in Penrith, Cumbria. He attended Cumbria College of Art and Design, now faculty of University of Cumbria, where he graduated with a degree in the theory and history of film with a side in performing arts.
At the age of 17, Hunnam was discovered in a shoe shop on Christmas Eve while drunkenly clowning around buying shoes for his brother. A production manager for the Newcastle-based children's show Byker Grove approached him and Hunnam was later cast in his first role as Jason in three episodes of the show. He also had a brief modeling career where he did a shoot for Kangols Caps and then decided modeling was not for him. Aged 18, his first major role came when he was cast by Russell T Davies as 15-year-old schoolboy Nathan Maloney in Davies' Channel 4 drama Queer as Folk.
He followed this up with his role as Daz in the film Whatever Happened to Harold Smith? (1999) and then moved to the US.
His career expanded to include a recurring role as Gregor Ryder in the WB series Young Americans. He then appeared in the short-lived Fox series Undeclared as an English drama student called Lloyd Haythe. Despite critical acclaim, the series was cancelled after one season. Hunnam then appeared on the large screen in Abandon (2002), Nicholas Nickleby (2002), and Cold Mountain (2003). Hunnam has stated that he does not wish to simply take any role that he is offered: "I have 60 years to make the money, but the choices I make in the next five years are really going to define my career." This decision resulted in his return to the UK to take the lead role of Pete Dunham in the film Green Street (2005), however his attempts at delivering a Cockney accent resulted in his inclusion in many critics' "worst accents in movie history" lists.
Hunnam says his role Patric, a member of "The Fishes", in Children of Men (2006), was the final part in his "trilogy of mad men". "I played the psycho in Cold Mountain, my character in Green Street is fairly psychotic and now I've got this role."
From 2008 to 2014, Hunnam starred as Jackson "Jax" Teller in Sons of Anarchy, a show about a prominent motorcycle club in a small fictional California town. Hunnam was cast after Kurt Sutter, the creator of the show, saw him in Green Street. His portrayal as Jax Teller has led Hunnam to receive a Critics' Choice Television Award nomination, three EWwy Award nominations for Best Lead Actor in a Drama series, and a PAAFTJ Award nomination for Best Cast in a Drama Series.
In 2011, Hunnam played the role of Gavin Nichols in the philosophical drama/thriller The Ledge by Matthew Chapman.
In 2012, he starred as the title character in the indie comedy 3,2,1... Frankie Go Boom alongside, among others, his Sons of Anarchy co-star Ron Perlman. Hunnam said that he considered the day that he filmed scenes with Perlman for that film the best and funniest day of filming he's ever had in his whole career. He also appeared as Jay, an ex-boxer, in Stefan Ruzowitzky's crime drama Deadfall (2012).
Hunnam starred as Raleigh Becket in Guillermo del Toro's sci-fi film Pacific Rim, that opened in July 2013 and grossed $411 million worldwide. It was announced on 2 September 2013 that Hunnam would play the lead role of Christian Grey in the film adaptation of E. L. James' novel Fifty Shades of Grey. However, on 12 October 2013, Universal Pictures announced that Hunnam had withdrawn from the film due to conflicts with the schedule of his series Sons of Anarchy.
On 2 June 2014, Hunnam was awarded a Huading Award for Best Global Emerging Actor, for his role as Raleigh in Pacific Rim, due to the film performing very well in the Asian markets. Hunnam reunited with del Toro in the horror film Crimson Peak, alongside Mia Wasikowska, Tom Hiddleston, and Jessica Chastain. The film began shooting in February 2014, and was released on 16 October 2015.
Hunnam starred as geographer Percy Fawcett in James Gray's adventure drama The Lost City of Z, which was filmed from August 2015 to October 2015, premiered at the New York Film Festival in 2016, and was released in April 2017. Hunnam also starred in Guy Ritchie's action-adventure film King Arthur: Legend of the Sword, which was filmed between March 2015 and July 2015, and was released in May 2017.
Immediately prior to getting cast on Sons of Anarchy, he sold his screenplay Vlad to Summit Entertainment with Brad Pitt's Plan B Studios co-producing. The film is being directed by music video director and photographer Anthony Mandler, and will focus on the real-life story of Vlad the Impaler. Hunnam learned the story from locals in Romania while shooting Cold Mountain. He stated that he had not acted in 18 months and was so broke that if he had not managed to sell the script he would have had to sell his house and move back to Britain to live with his mother. Hunnam is also developing a screenplay based on a 2011 Rolling Stone article that he optioned about Edgar Valdez Villareal, an American drug lord who ran one of the biggest cartels in Mexico. Another project he has in development is a film about gypsy culture in Britain, which he hopes to direct. He stated that it's "a part of English society that's really seldom been explored, but is one of the most colourful and interesting parts of British society."
In 1999, Hunnam met actress Katharine Towne when they both auditioned for roles on Dawson's Creek. After dating for three weeks, they married in Las Vegas. They divorced in 2002. Hunnam has been dating artist Morgana McNelis since 2005.