Clive Owen as Arthur

Ioan Gruffudd as Lancelot

Keira Knightley as Guinevere

Mads Mikkelsen as Tristan

Joel Edgerton as Gawain

Hugh Dancy as Galahad

Ray Winstone as Bors

Stephen Dillane as Merlin

Ray Stevenson as Dagonet

Til Schweiger as Cynric

Stellan Skarsgård as Cerdic

Sean Gilder as Jols

Ken Stott as Marius Honorius

Charlie Creed-Miles as Ganis

David Murray as Merlin's Lieutenant

Ned Dennehy as Mental Monk

Phelim Drew as Obnoxius Monk

Des Braiden as Third Monk

Bosco Hogan as Bishop Decoy

David Wilmot as Woad Killed by Lancelot

Lochlann Ó Mearáin as Roman Commander

Ivano Marescotti as Bishop Germanus

Clive Russell as Lancelot's Father

Graham McTavish as Roman Officer

Dessie Gallagher as Mercenary

Elliot Henderson-Boyle as Young Lancelot

Owen Teale as Pelagius (uncredited)

Dawn Bradfield as Vanora

Pat Kinevane as Horton

Paul Tall-Order Ritchie as Saxon (uncredited)