The hit BBC One show will bow out with a two-part special, airing this Christmas.
Co-creators and executive producers Johnny Capps and Julian Murphy confirmed in a statement that the fifth series of the show would be its last, saying: "This is the series where the storylines truly reach their apex.
"We always felt the story of the legend was best told across five series, leading to a spectacular finale that draws on the best known elements of this much-loved story and brings to a conclusion the battle for Camelot.
"We'd like to thank the amazing cast and crew for their professionalism and dedication, the BBC, FME and all of our partners globally for their incredible support and encouragement across the last five series. But chiefly, our thanks go to Merlin's remarkable and loyal audience around the world for their enthusiasm for the characters and Camelot universe."