The Century 21 Organisation was a group of companies founded by Gerry Anderson in the early 1960s to expand on his television production company, AP Films (APF; later Century 21 Productions). In addition to APF, the group included:

• a property licensing company, AP Films (Merchandising) – established in 1960 as an APF subsidiary, later Century 21 Merchandising;^[4]
• a record label, Century 21 Records (established in 1964)^[5] – a joint venture with Pye Records, producing soundtracks and tie-in audiobooks;
• a toy manufacturer, Century 21 Toys (established in 1966) – formed by Century 21's acquisition of toymakers J. Rosenthal;^[6][7]
• a publishing company, Century 21 Publishing or Century 21 Publications (established in 1966).^[1] In partnership with City Magazines, it created the comics titles TV Century 21 and Lady Penelope, among others. It also published tie-in novels through Armada Books.^[8]

Most of the companies' activities were marketing of products created by Century 21 Productions — in particular the TV series Thunderbirds, Captain Scarlet and the Mysterons and Joe 90,^[9] although some spin-off media were based on characters and machines from other media franchises, often connected to Lew Grade's ITC Entertainment.

The various "Century 21" brands predate Century 21 Productions — immediately following completion and the first TV screening of Thunderbirds, AP Films was renamed Century 21 Productions to align it with its growing merchandising sister companies Century 21 Merchandising, Century 21 Toys, Century 21 Records,^[10] and Century 21 Publishing.

By the beginning of 1969, Century 21 Productions had become financially over-stretched. Within a few months, they had disbanded their three warehouse-sized studios on the Slough Trading Estate.

From 1965 to 1969, Century 21 Publishing partnered with the published City Magazines to produce weekly comics titles based on Anderson's Supermarionation properties. Century 21 packaged the comics, hiring the editors, writers and artists, which were then printed and distributed by City Magazines. The imprint's most prominent and long-running titles were TV Century 21 (later known as TV21) and Lady Penelope; three other related titles — Solo, TV Tornado, and Joe 90 Top Secret — eventually merged into TV21.

Century 21 Merchandising acquired a line of plastic science fiction toys manufactured in Hong Kong, which they marketed under the name Project SWORD. Although not based on Anderson's creations, Project Sword did feature in two series of comic strips and text stories published by City Magazines/Century 21 Publishing. The only Anderson craft made by the line was a model of Zero-X, the spacecraft which first appeared in the film Thunderbirds Are Go.^[11] A comic strip series based on the toys appeared in the short-lived comic Solo. After Solo was merged into TV21, a second series of stories — text, illustrated by comics artists such as Ron Embleton and Don Lawrence — appeared. The publisher also released a Project SWORD annual, featuring text and comic strips.^[11]

In June 1969 the entire staff of Century 21 Publishing were given a month's notice. A small nucleus of staff from the disbanded division were taken on by Leonard Matthews^[12] and Alf Wallace — the ex-managing editors of Fleetway Juvenile Comics; and Eagle and Odhams' Power Comics line, respectively — who were now operating an independent studio off Fleet Street under the name of Martspress.^[12] Martspress packaged the relaunched version of TV21 which soon phased out the Anderson-related content.