Jonestown was the informal name for the "Peoples Temple Agricultural Project", an intentional community in northwestern Guyana formed by the Peoples Temple, an American cult led by Jim Jones. It became internationally notorious when, on November 18, 1978, 918 people died in the settlement as well as in a nearby airstrip and in Georgetown, Guyana's capital. The name of the settlement became synonymous with the incidents at those locations.
A total of 909 Temple members died in Jonestown, all but two from apparent cyanide poisoning, in an event termed "revolutionary suicide" by Jones and some members on an audio tape of the event and in prior discussions. The poisonings in Jonestown followed the murder of five others by Temple members at a nearby Port Kaituma airstrip. The victims included Congressman Leo Ryan, the first and only Congressman murdered in the line of duty in the history of the United States. Four other Temple members died in Georgetown at Jones' command.
To the extent the actions in Jonestown were viewed as a mass suicide, it is the largest such event in modern history and resulted in the largest single loss of American civilian life in a non-natural disaster until the events of September 11, 2001.