Peter Sellers

as Grand Duchess Gloriana XII / Prime Minister Count Rupert Mountjoy / Tully Bascombe

Jean Seberg

as Helen Kokintz

William Hartnell

as Will Buckley

David Kossoff

as Professor Alfred Kokintz

Leo McKern

as Benter

MacDonald Parke

as General Snippet

Austin Willis

as United States Secretary of Defense

Timothy Bateson

as Roger