The Gulf of Tonkin Resolution or the Southeast Asia Resolution, Pub. L.Tooltip Public Law  88–408, 78 Stat. 384, enacted August 10, 1964, was a joint resolution that the United States Congress passed on August 7, 1964, in response to the Gulf of Tonkin incident.

The Gulf of Tonkin incident was an international confrontation that led to the United States engaging more directly in the Vietnam War. It consisted of a confrontation on August 2, 1964, when United States forces were carrying out covert amphibious operations close to North Vietnamese territorial waters, which triggered a response from North Vietnamese forces. The United States government falsely claimed that a second incident occurred on August 4, 1964, between North Vietnamese and United States ships in the waters of the Gulf of Tonkin. Originally, US military claims blamed North Vietnam for the confrontation and the ostensible, but in fact imaginary, incident on August 4. Later investigation revealed that the second attack never happened. The official American claim is that it was based mostly on erroneously interpreted communications intercepts. The National Security Agency, an agency of the US Defense Department, had deliberately skewed intelligence to create the impression that an attack had been carried out.