Stasi, official name Ministerium für Staatsicherheit (German: "Ministry for State Security"), secret police agency of the former German Democratic Republic (East Germany). The Stasi was one of the most hated and feared institutions of the East German communist government.

The Stasi developed out of the internal security and police apparatus established in the Soviet zone of occupation in Germany after World War II. The law establishing the ministry, whose forerunner was the Kommissariat 5 (modeled along the lines of the Soviet KGB), was passed by the East German legislature on February 8, 1950.

During Germany's partition East Germany's Ministry of State Security (MfS) was one of the largest intelligence and security services in the world. Known as the Stasi by East Germans, it used some 90,000 regular employees—and nearly double that number of informers—to surveil the country's 17 million people.