Robert Rietti, ORI (born Lucio Herbert Rietti; 8 February 1923 – 3 April 2015), was an English actor, voice actor, playwright and recording director of Italian descent. With over 200 credits to his name, he had a highly prolific career in the American, British and Italian entertainment industries, supervising in and participating in the post-production dubbing both foreign and domestic, often overseeing the English-language dubbing of foreign actors' dialogue.
In radio, he teamed up with Orson Welles in the radio series The Third Man (1951), and then again on the popular series The Black Museum (1952), which was broadcast to the US Armed Forces. This was to be the beginning of many collaborations between Rietti and Orson Welles, who remained close friends. He was also a regular on the radio series Horatio Hornblower (1952) with Michael Redgrave, The Scarlet Pimpernel (1952), Theatre Royal (1954) with Sir Laurence Olivier, and the classic Sherlock Holmes (1954) with John Gielgud and Ralph Richardson.
In The Prisoner, Robert Rietti provided the voice of Number Two during the opening credits montage when the actors playing Number Two were unavailable to provide their own voice for a loop.