Charlie Hunnam as Arthur

Jude Law as Vortigern

Astrid Bergès-Frisbey as The Mage

Eric Bana as Uther Pendragon

Djimon Hounsou as Bedivere

Aidan Gillen as William "Goosefat Bill"

Kingsley Ben-Adir as Tristan "Wet Stick"

Neil Maskell as Back Lack

Craig McGinlay as Percival "Percy"

Tom Wu as "Kung Fu" George

Freddie Fox as Rubio

Mikael Persbrandt as Greybeard

Peter Ferdinando as Earl of Mercia

Geoff Bell as Mischief John

Annabelle Wallis as Maggie

Katie McGrath as Elsa

Lorraine Bruce as Syren 1

Eline Powell as Syren 2

Hermione Corfield as Syren 3

Bleu Landau as Blue

Poppy Delevingne as Igraine

Millie Brady as Catia

Zac Barker as Young Arthur 2 Yrs

Oliver Barker as Young Arthur 2 Yrs

Nicola Wren as Lucy

Wil Coban as Brother Blackleg

Jacqui Ainsley as Lady of the Lake

Georgina Campbell as Kay

Rob Knighton as Mordred

Michael Hadley as Mage King

David Beckham as Trigger

Alan Turkington as General 1

Michael McElhatton as Jack's Eye

Charlie Rawes as Axeman

James Warren as Mike

Ellie Graham as Maria

Kamil Lemieszewski as Merlin

Kalle Hennie as Viking

Peter Guinness as Baron 1

Mark Umbers as Baron 2

Adrian Bouchet as Baron 3

Florence Bell as Woman 1

Anna Brooks Beckman as Woman 2

Cordelia Bugeja as Woman 3

Rebecca Calder as Maid 1

Lee Nicholas Harris as Dan Clan Mafia (uncredited)

Gintare Beinoraviciute as Noble (uncredited)

Alice E. Mayer as Noble Girl (uncredited)

Claira Watson Parr as Noblewoman (uncredited)

Alphonso Austin as Slave Labourer (uncredited)

Rudy Barrow as Londinium Fighter (uncredited)

Daniel Stisen as SPAC / Londinum Fighter (uncredited)

Joel Bryant as Londinium Fighter (uncredited)

Dacio Caballero as Fighter (uncredited)

Lucy Chappell as Young Mother (uncredited)

Jamie B. Chambers as Knight (uncredited)

Pedro Caxade as Vortigern's Guard (uncredited)

Nick Cornwall as Clan Head 1 (uncredited)

Steve Barnett as Brothel Punter (uncredited)

Guy Ritchie as Inn Owner

Steen Young as Nemesis (uncredited)

Jason Lines as Miscellaneous (uncredited)

Tom Coulston as Pendragon Soldier

Sarah-Jane De Crespigny as Low-Rent Villager