Main •
Joseph Fiennes as
Merlin – the creator and custodian of the legend of Camelot. As Arthur's greatest and most powerful ally, Merlin believes in him even more than Arthur believes in himself. He can foresee the threats to Arthur more clearly than anyone, but he must fight the dark nature of his power and harness it to bring forth a new Camelot. •
Jamie Campbell Bower as
King Arthur – a handsome, carefree young man. He is torn from his home and family upon learning he is the only male heir to the throne as a result of
the king's untimely death. Arthur's intense education in a dark, unruly world inspires him to pursue a kingdom based on justice, hope, and freedom from tyranny while the lands he oversees are corrupted by violence, greed, and despair. •
Eva Green as
Morgan Pendragon – the beautiful and ruthlessly ambitious daughter of King Uther. She wishes to claim her right to her father's throne, but she does not count on Merlin's plans or the existence of Arthur, her newly revealed half-brother. In her pursuit of power and revenge, Morgan gives herself over to dark forces that allow her to threaten the court of Camelot from within. She functions as the main antagonist of the series. •
Tamsin Egerton as
Guinevere – an ambitious and strong willed woman, making her a source of great support and strength to Arthur as he grows into his role as king. Although she is married to Leontes, one of Arthur's most loyal knights, she cannot deny the attraction she and Arthur feel for each other. •
Claire Forlani as
Igraine – Arthur's biological mother and second wife of King Uther. She is estranged from her son and despised by her step-daughter Morgan. She has lived a life of deep pain and agony, but has never lost her faith or her heart. Igraine quickly becomes an ally and figure of strength for Arthur and the entire court of Camelot. •
Chipo Chung as
Vivian – a young woman who is descended from a people brought to Britain as slaves. She served as an indentured servant at Uther's court and now works as an attendant and messenger for Morgan. •
Sinéad Cusack as
Sybil – a nun who has raised Morgan and comes to live with her. She is a motherly figure for Morgan, acting as her advisor in matters both political and supernatural. She takes the blame for Morgan's treason, and is beheaded by Gawain. •
Peter Mooney as
Kay – Arthur's fiercely loyal older brother. Kay encourages Arthur to take up his destiny as King of Britain. As the king's Marshal, Kay has the freedom to become his own man, but will always remain Arthur's older brother and closest friend. •
Clive Standen as
Gawain – a former knight and great warrior. He has become disillusioned and lost his way in life. Kay and Leontes recruit him to join the court of Camelot. He eventually comes to Camelot and realizes Arthur is different and not just another warlord. Inspired, he finds reason to fight and train Arthur's men. •
Philip Winchester as Leontes – one of King Uther's bravest knights. Leontes pledges his loyalty to the new king after Uther's death and joins Arthur in Camelot. Married to Guinevere, his loyalty and experience are invaluable to the young king as he attempts to secure order in a land beset by violence and threats from rivals to the throne.
Recurring •
Sebastian Koch as
King Uther, Arthur's biological father who was poisoned and killed by Morgan. •
James Purefoy as
King Lot, a warrior-king who forms an alliance with Morgan. • Diarmaid Murtagh as Brastias, a knight of King Arthur. • Jamie Downey as Ulfius, a knight of King Arthur, who is killed during the battle at Bardon Pass. •
Daragh O'Malley as
Leodegrance, Guinevere's father. •
Sean Pertwee as
Sir Ector, Arthur's foster father and Kay's father. •
Lara Jean Chorostecki as Bridget, Guinevere's cousin. == Episodes ==