Red Rackham's Treasure (French: Le Trésor de Rackham le Rouge) is the twelfth volume of The Adventures of Tintin, the comics series by Belgian cartoonist Hergé. The story was serialised daily in Le Soir, Belgium's leading francophone newspaper, from February to September 1943 amidst the German occupation of Belgium during World War II. Completing an arc that begun in The Secret of the Unicorn, the story tells of young reporter Tintin and his friend Captain Haddock as they launch an expedition to the Caribbean to locate the treasure of the pirate Red Rackham.

Red Rackham's Treasure was a commercial success and was published in book form by Casterman the year following its conclusion. Hergé continued The Adventures of Tintin with The Seven Crystal Balls, while the series itself became a defining part of the Franco-Belgian comics tradition. Red Rackham's Treasure has been cited as one of the most important installments in the series for marking the first appearance of eccentric scientist Cuthbert Calculus, who subsequently became a core character. The story was adapted for the 1957 Belvision animated series Hergé's Adventures of Tintin, the 1991 Ellipse/Nelvana animated series The Adventures of Tintin, the 1992-3 BBC Radio 5 dramatisation of the Adventures, the feature film The Adventures of Tintin (2011) directed by Steven Spielberg, and the film's tie-in video game.

Tintin and his friend Captain Haddock plan an expedition to the West Indies aboard a fishing trawler, the Sirius, to search for the treasure of the pirate Red Rackham. Having previously read three parchments authored by Haddock's ancestor, Sir Francis Haddock, the duo had discovered the coordinates to what they believe is the treasure aboard the sunken 17th century vessel, the Unicorn, near an unknown island. An eccentric, hard-of-hearing inventor named Professor Cuthbert Calculus offers to aid them with the use of his shark-shaped one-man submarine, but they decline his assistance. Setting sail, they are joined by the police detectives Thomson and Thompson and soon discover that Calculus has stowed away on board, bringing his submarine with him.

When they reach the coordinates shown on the parchments, there is no island in sight. Frustrated, Haddock ponders turning back, but Tintin soon realizes the problem: If Sir Francis had used a French chart instead of an English chart to calculate the position, the coordinates would have been measured on the Paris Meridian rather than the Greenwich Meridian. As they have been using the Greenwich Meridian, they realise that they are too far west.

After traveling to the correct position, they discover an uncharted island, which is located about 230 km (140 mi) north of Punta Cana (Dominican Republic) and 286 km (178 mi) East-South-East of Cockburn Town (location of 20°37'42.0"N 70°52'15.0"W, adjusted by 2° 20' 14.02500" E for the Paris Meridian). There, they find a statue of Sir Francis Haddock and other evidence, including parrots who still use Haddock insults handed down from Sir Francis. Tintin deduces that Francis Haddock had taken refuge on the island and that the wreck of the Unicorn must be nearby. They locate the wreck using Calculus' submarine and recover various artefacts from it, but do not find the treasure. Among the artefacts is a strongbox containing old documents revealing that Sir Francis Haddock had been the owner of the country estate Marlinspike Hall.

Back in Belgium, Calculus purchases the Hall, using funds from the sale of his submarine design, and gives it to Haddock. Tintin and Haddock search the house's cellars, where Tintin spots a statue of Saint John the Evangelist holding a cross with a globe and eagle at its feet. Tintin suddenly remembers that Francis Haddock's original three parchments said, "For 'tis from the light that light will dawn, and then shines forth the Eagle's cross" and realises that this message referred, not to the location of the Unicorn, but to Saint John "the eagle": his traditional symbol. Tintin locates the island on the globe, presses a secret button which he finds there, and discovers Red Rackham's treasure hidden inside. Sometime later, Haddock hosts an exhibition of the treasure and several Unicorn artefacts in Marlinspike Hall.

Red Rackham's Treasure was serialized amidst the German occupation of Belgium during World War II. Hergé had accepted a position working for Le Soir, Belgium's largest Francophone daily newspaper. Confiscated from its original owners, Le Soir was permitted by the German authorities to reopen under the directorship of Belgian editor Raymond de Becker, although it remained firmly under Nazi control, supporting the German war effort and espousing anti-Semitism. After joining Le Soir on 15 October 1940, Hergé became editor of its new children's supplement, Le Soir Jeunesse, with the help of an old friend, Paul Jamin, and the cartoonist Jacques Van Melkebeke, before paper shortages forced The Adventures of Tintin to be serialised daily in the main pages of Le Soir. Some Belgians were upset that Hergé was willing to work for a newspaper controlled by the occupying Nazi administration, although he was heavily enticed by the size of Le Soir's readership, which numbered some 600,000. Faced with the reality of Nazi oversight, Hergé abandoned the overt political themes that had pervaded much of his earlier work, instead adopting a policy of neutrality. Entertainment producer and author Harry Thompson observed that, without the need to satirise political types, "Hergé was now concentrating more on plot and on developing a new style of character comedy. The public reacted positively".

Red Rackham's Treasure was the second half of a two-part story arc which had begun with the previous adventure, The Secret of the Unicorn. This arc was the first that Hergé had produced since Cigars of the Pharaoh and The Blue Lotus (1934–36). However, as Tintin expert Michael Farr related, whereas Cigars of the Pharaoh and The Blue Lotus had been largely "self-sufficient and self-contained", the connection between The Secret of the Unicorn and Red Rackham's Treasure is far closer.