Merlin (also known as The Adventures of Merlin) is a British fantasy-adventure drama television programme, loosely based on the Arthurian legends regarding the close relations of Merlin and King Arthur. Created by Julian Jones, Jake Michie, Johnny Capps and Julian Murphy for the BBC, it was broadcast for five series on BBC One between 20 September 2008 and 24 December 2012. The programme starred Colin Morgan, Bradley James, Katie McGrath, Angel Coulby, Richard Wilson, Anthony Head and John Hurt.

The programme is a reimagining of the legend, in which young warlock Merlin is sent to the kingdom of Camelot by his mother because of his "special gift". After saving Prince Arthur's life in the first episode, he becomes Arthur's manservant. Merlin soon learns that the reason for his gift is to protect Arthur, but Merlin must hide his powers because magic was banned in Camelot by Arthur's father, King Uther Pendragon, and those caught practising it are executed. Over the years and after several adventures together, Merlin and Arthur become trusted friends and companions, with the former doing his best to influence the latter into becoming the king he is destined to be.

Merlin was nominated for several awards, winning the 2011 British Academy Television Award for best visual effects. Broadcasting rights were sold to over 180 countries.

Merlin (Colin Morgan) is a young, powerful warlock who arrives in the kingdom of Camelot after his mother arranges for him to stay with the court physician, Gaius (Richard Wilson). He discovers that the king, Uther Pendragon (Anthony Head), outlawed magic twenty years earlier in an event known as the Great Purge and imprisoned the last dragon, Kilgharrah (voice of John Hurt), in the caves beneath the castle. After hearing a mysterious voice inside his head, Merlin makes his way to the cavern beneath the keep to find that he was hearing the dragon's voice. The Great Dragon tells Merlin that he has an important destiny: to protect Uther's only son, Prince Arthur (Bradley James), who will return magic to Camelot and unite the land of Albion.

When Merlin meets Arthur, Merlin considers him to be an arrogant bully, and Arthur, likewise, is less than impressed with Merlin. After saving the prince's life, Merlin is appointed as his personal manservant. The two experience many adventures, over the course of which they come to respect and trust one another. But when Uther's actions eventually cause his ward, Morgana (Katie McGrath), to turn against Camelot and pursue a path of evil, Merlin and Arthur must join forces with friends, old and new, to protect their home and secure their destinies.

The programme was conceived by Julian Murphy and Johnny Capps. The BBC had been keen on showing a drama based on the character of Merlin for some time. A year before the Shine series was initiated, writer and producer Chris Chibnall had been developing a project aimed at a BBC One Sunday night slot, but this was ultimately not commissioned. The Shine version of the project was put into development in late 2006, commissioned by Controller of BBC One Peter Fincham and BBC Head of Fiction Jane Tranter, with Fincham keen on having more series on his channel which embodied "three generation TV – that's TV you can watch with your grandparents and children. There's not enough of that about."

The series went into production in March 2008, with filming in Wales and France (at the Château de Pierrefonds). Two Kent locations were also used: The Barons Hall and Garden Tower at Penshurst Place, and Chislehurst Caves for the first series. The series was produced by Shine in association with BBC Wales, whose Head of Drama Julie Gardner was executive producer for the BBC. Doctor Who's chief writer Russell T Davies had been an important influence on the tone and style of Merlin. CGI special effects for the series were provided by Colin Gorry Effects and The Mill. The Old English for spells was written by university scholar and medievalist Dr. Mark Faulkner, and later by the script editing team.

Capps and Murphy confirmed on 24 July 2011 that BBC had commissioned a fifth series. Filming for the fifth series began March 2012 in Pierrefonds, France and near Cardiff, Wales. 13 episodes were ordered. On 26 November 2012, it was announced that series 5 of Merlin would be the last, with a two-part special concluding the series over Christmas.