The Blue Lotus (French: Le Lotus bleu) is the fifth volume of The Adventures of Tintin, the comics series by Belgian cartoonist Hergé. Commissioned by the conservative Belgian newspaper Le Vingtième Siècle for its children's supplement Le Petit Vingtième, it was serialised weekly from August 1934 to October 1935 before being published in a collected volume by Casterman in 1936. Continuing where the plot of the previous story, Cigars of the Pharaoh, left off, the story tells of young Belgian reporter Tintin and his dog Snowy, who are invited to China in the middle of the 1931 Japanese invasion, where Tintin reveals the machinations of Japanese spies and uncovers a drug-smuggling ring.

In creating The Blue Lotus, Hergé exhibited a newfound emphasis on accuracy and documentation in his portrayal of foreign societies. He was heavily influenced by his close friend Zhang Chongren, a Chinese student studying in Belgium, and the work both satirises common European misconceptions about China as well as criticising the actions of the Japanese invaders. The Blue Lotus was a commercial success in Belgium and was soon serialised in France and Switzerland, while news of the book led to the Chinese political leader Chiang Kai-shek inviting Hergé to visit China itself. Hergé continued The Adventures of Tintin with The Broken Ear, while the series itself became a defining part of the Franco-Belgian comics tradition. In 1946, The Blue Lotus was partially re-drawn and coloured by the cartoonist and his team of assistants; during this process a number of minor plot elements were changed. The adventure introduces the recurring characters J.M. Dawson and Chang Chong-Chen. The story was adapted for a 1991 episode of the Ellipse/Nelvana animated series The Adventures of Tintin. Critical analysis of the story has been positive, with various commentators considering it to be one of Hergé's finest works.

Staying at the palace of the Maharaja of Gaipajama in India, Tintin is approached by a visitor from Shanghai in China. The visitor supplies him with the name of Mitsuhirato, a Japanese businessman based in Shanghai while on secondment, but before finishing his message is hit by a dart dipped in Rajaijah, the "poison of madness". Tintin and his fox terrier Snowy travel to Shanghai to meet Mitsuhirato, who warns them that the Maharajah is in danger and that they should return to India. Surviving several attempts on his life by mysterious assailants, Tintin attempts to leave for India by boat, but is kidnapped and brought back to China. His abductors reveal themselves as members of a secret society known as the Sons of the Dragon, who, like the Maharaja, are devoted to combating the opium trade. Their leader, Wang Chen-Yee, explains to Tintin that Mitsuhirato is both a Japanese spy and an opium smuggler, and enlists Tintin in their fight to stop him. Tintin agrees, and spies on Mitsuhirato at the Blue Lotus opium den. Following him, Tintin witnesses Mitsuhirato blowing up a Chinese railway (an action loosely based on the Mukden Incident). The Japanese government frames it as an attack from Chinese bandits, and uses it as an excuse to invade Northern China, taking Shanghai under its control.

Tintin is captured by Mitsuhirato, who plans to poison him with Rajaijah. However, one of Wang's agents swaps out the poison for coloured water, so when Tintin is "poisoned", he is able to feign madness long enough to be untied and let go so he is able to escape from Mitsuhirato. Mitsuhirato later discovers the deception and convinces the Japanese military forces to put a warrant out for Tintin's arrest. Meanwhile, Tintin enters the Shanghai International Settlement in search for Professor Fang Hsi-ying, an expert on poisons who he hopes can develop a cure for Rajaijah, but discovers that he has been kidnapped. J.M. Dawson, the Settlement's corrupt Chief of Police, arrests Tintin and hands him over to the Japanese, who sentence him to death before he is rescued by Wang.

Travelling to Hukow to search for Fang, Tintin comes across a flood that has caused extensive damage, and rescues a young Chinese orphan Chang Chong-Chen from drowning. Chang accompanies Tintin to Hukow, where one of Mitsuhirato's spies tries to kill Tintin but fails; they realise that it was a trap and that Fang was not there. Meanwhile, the detectives Thomson and Thompson are employed by Dawson to arrest Tintin, but fail on multiple occasions. Returning to Shanghai, Tintin intends to confront Mitsuhirato, and allows himself to be captured by him. Being held prisoner at The Blue Lotus, he discovers that Mitsuhirato is in league with the film director Rastapopoulos, who reveals that he is the leader of the international opium smuggling gang that Tintin has been pursuing in Egypt, Arabia, India, and now China. Rastapopoulos was also the man assumed to have fallen to his death during the foiled kidnapping of the Maharaja's son. However, in accordance with Tintin's plan, Chang and the Sons of the Dragon rescue Tintin and Fang; Rastapopoulos is arrested while Mitsuhirato commits seppuku. Tintin's report on Mitsuhirato's activities leads to accusations against Japan, which withdraws from the League of Nations in protest. Fang develops a cure for Rajaijah, while Wang adopts Chang as his son. Tintin and Snowy return home to Europe.

Georges Remi—best known under the pen name Hergé—was employed as editor and illustrator of Le Petit Vingtième ("The Little Twentieth"), a children's supplement to Le Vingtième Siècle ("The Twentieth Century"), a staunchly Roman Catholic, conservative Belgian newspaper based in Hergé's native Brussels which was run by the Abbé Norbert Wallez. In 1929, Hergé began The Adventures of Tintin comic strip for Le Petit Vingtième, about the exploits of fictional young Belgian reporter Tintin. Wallez ordered Hergé to set his first adventure in the Soviet Union to act as anti-socialist propaganda for children (Tintin in the Land of the Soviets), to set his second adventure in the Belgian Congo to encourage colonial sentiment (Tintin in the Congo), and to set his third adventure in the United States to use the story as a denunciation of American capitalism (Tintin in America). On 24 November 1932, Le Petit Vingtième published a fictional interview with Tintin in which the reporter announced that he would travel to China via Egypt, India, Sri Lanka, and Indochina. This plotline resulted in Tintin in the Orient, the first part of which was an Adventure set in Egypt, Arabia, and India that Hergé later titled Cigars of the Pharaoh. Cigars ceased publication in Le Petit Vingtième in February 1934, and Hergé next provided the standalone story Popol out West for the newspaper. The Blue Lotus was the second half of the Tintin in the Orient story that Hergé had begun with Cigars of the Pharaoh.

However, Hergé knew as little about China as he did about the Soviet Union or the Belgian Congo. At the time most Belgians held to a negative stereotype of China, viewing it as "a distant continent of a nation, barbaric, overpopulated, and inscrutable", and Hergé had long believed this view. He had included Chinese characters in two previous Adventures, in both instances depicting them according to traditional European clichés. In Tintin in the Land of the Soviets, he included two pigtailed Chinese men hired by the Bolsheviks to torture Tintin, while in Tintin in America he featured two Chinese hoodlums who plotted to eat Snowy. Hergé learned a bit about the country from Albert Londres' book China Madness, based on Londres' experiences in the country. He was also influenced in his portrayal of China by the 1933 German film Flüchtlinge (At the End of the World).

"It was at the time of The Blue Lotus that I discovered a new world. For me up to then, China was peopled by a vague, slit-eyed people who were very cruel, who would eat swallows' nests, wear pig-tails and throw children into rivers... I was influenced by the pictures and stories of the Boxer Uprising, where the accent was always on the cruelty of the yellow people, and this made a deep impact".