Thuggee (UK: /θʌˈɡiː/, US: /ˈθʌɡi/) was a network of organized crime in British Raj India in the 19th century of gangs that traversed the Indian subcontinent murdering and robbing people. A member of Thuggee was referred to as a Thug.

The Thugs were purported to have murdered their victims by strangling using a bandana as a tool. The Thugs were believed to practice their killings as a form of worship toward the goddess Kali. For centuries, the authorities of the Indian subcontinent, such as the Khalji dynasty, the Mughal Empire, and the British Raj, attempted to curtail the criminal activities of Thuggee during their rule.

Contemporary scholarship is increasingly skeptical of the thuggee concept, and has questioned the existence of such a phenomenon, which has led many historians to describe thuggee as the invention of the British colonial regime. Jonathan Perris has argued that early stories about Thuggee had less to do with Indian social history than with the literary culture of London at the time.

ठग (Thug), translated from Hindi as 'swindler' or 'deceiver'. It is related with the verb thugna ('to deceive'), from the Sanskrit स्थग (sthaga 'cunning, sly, fraudulent') and स्थगति (sthagati, 'he conceals'). This term, describing the murder and robbery of travellers, was popular in the northern parts of the Indian subcontinent, especially the northern and eastern regions of India. The English word thug is from the same roots.

The Thuggee reportedly operated as gangs of highwaymen who tricked and murdered their victims by strangling. To take advantage of their victims, the thugs would join travellers and gain their confidence, which would allow them to surprise and strangle the travellers with a handkerchief or noose. One of the Thuggee would befriend their potential targets (even to the point of assuming their religion) and accompany them for a while to assess their potential wealth. Eventually, as one Thug managed to distract their victims by engaging them in conversation, the other members who were tasked with the killing would strangle them swiftly from behind. After the murder, they sometimes mutilated the corpses to hide evidence, and buried the remains. Their modus operandi led to the thugs being called Phansigar ("using a noose"), a term more commonly used in southern India.

Although strangulation is one of their most-recognised methods of murder, they also used blades and poison. The Thuggee gangs usually commenced their act in the evening, and attacked travelling groups whose numbers were smaller than their own groups to avoid unnecessary losses. To avoid suspicion, they carried only a few swords. The poisonous ingredients which were prepared by the Thuggee consisted of Datura metel, the Indian thornapple (family Solanaceae). A poisonous plant with powerful deliriant properties and sacred to Shiva, it was sometimes used by thugs to induce drowsiness or stupefaction, making strangulation easier. The Hindi name for the plant धतूरा (dhatūra) is derived from Sanskrit and was adapted by Linnaeus into the Latinate genus name Datura.

A leader of a Thuggee was called jemadar. This was derived from military-style ranks such as jemadar and subedar among Thugs as well as reference to individual members as a "private", suggests that the organisation of their gangs had a military link. They used a jargon known as Ramasee to disguise their true intentions from their targets. The Thuggee members comprised some who had inherited Thuggee as a family vocation, and others who were forced to turn to it out of necessity. The leadership of many of the groups tended to be hereditary with family members sometimes serving together in the same band. Such thugs were known as aseel. According to a Thuggee testimony, a young initiate who joined the group was usually trained by a senior experienced Thuggee member who held the title of guru. While they usually kept their acts a secret, female thugs also existed and were called baronee in Ramasee, while an important male Thuggee was called baroo.

The Thuggee usually avoided killing the children of the victims and instead adopted them. However, sometimes they resorted to killing women and children to eliminate witnesses. Some of the thugs avoided murdering victims they considered proscribed according to their beliefs and let other unscrupulous members commit the murder or were forced to let them by those who did not believe in their customs like the Muslim thugs. Many of them avoided committing the robberies near the areas in which they lived, to avoid recognition and criminal repercussion.