The Warsaw Ghetto (German: Warschauer Ghetto, officially Jüdischer Wohnbezirk in Warschau, 'Jewish Residential District in Warsaw'; Polish: getto warszawskie) was the largest of the Nazi ghettos during World War II and the Holocaust. It was established in November 1940 by the German authorities within the new General Government territory of occupied Poland. At its height, as many as 460,000 Jews were imprisoned there, in an area of 3.4 km² (1.3 sq mi), with an average of 9.2 persons per room, barely subsisting on meager food rations. Jews were deported from the Warsaw Ghetto to Nazi concentration camps and mass-killing centers. In the summer of 1942, at least 254,000 ghetto residents were sent to the Treblinka extermination camp during Großaktion Warschau under the guise of "resettlement in the East" over the course of the summer. The ghetto was demolished by the Germans in May 1943 after the Warsaw Ghetto Uprising had temporarily halted the deportations. The total death toll among the prisoners of the ghetto is estimated to be at least 300,000 killed by bullet or gas, combined with 92,000 victims of starvation and related diseases, the Warsaw Ghetto Uprising, and the casualties of the final destruction of the ghetto.

Before World War II, the majority of Polish Jews lived in the merchant districts of Muranów, Powązki, and Stara Praga. Over 90% of Catholics lived further away from the commercial center. The Jewish community was the most prominent there, constituting over 88% of the inhabitants of Muranów; with the total of about 32.7% of the population of the left-bank and 14.9% of the right-bank Warsaw, or 332,938 people in total according to 1931 census. Many Jews left the city during the Great Depression. Antisemitic legislation, boycotts of Jewish businesses, and the nationalist "endecja" post-Piłsudski Polish government plans put pressure on Jews in the city. In 1938, the Jewish population of the Polish capital was estimated at 270,000 people.

The Siege of Warsaw continued until September 29, 1939. On September 10 alone, the Luftwaffe conducted 17 bombing raids on the city; three days later, 50 German planes attacked the city center, targeting specifically Wola and Żoliborz. In total, some 30,000 people were killed, and 10 percent of the city was destroyed. Along with the advancing Wehrmacht, the Einsatzgruppe EG IV and the Einsatzkommandos rolled into town. On November 7, 1939, the Reichsführer-SS reorganized them into local Security Service (SD). The commander of EG IV, Josef Meisinger (the "Butcher of Warsaw"), was appointed chief of police for the newly formed Warsaw District.

By the end of the September campaign, the number of Jews in and around the capital increased dramatically with thousands of refugees escaping the Polish-German front. In less than a year, the number of refugees in Warsaw exceeded 90,000. On October 12, 1939, the General Government was established by Adolf Hitler in the occupied area of central Poland. The Nazi-appointed Jewish Council (Judenrat) in Warsaw, a committee of 24 people headed by Adam Czerniaków, was responsible for carrying out German orders. On October 26, the Jews were mobilized as forced laborers to clear bomb damage and perform other hard labor. One month later, on November 20, the bank accounts of Polish Jews and any deposits exceeding 2,000 zł were blocked. On November 23, all Jewish establishments were ordered to display a Jewish star on doors and windows. Beginning December 1, all Jews older than ten were compelled to wear a white armband, and on December 11, they were forbidden from using public transit. On January 26, 1940, the Jews were banned from holding communal prayers due to "the risk of spreading epidemics." Food stamps were introduced by the German authorities, and measures were stepped up to liquidate all Jewish communities in the vicinity of Warsaw. The Jewish population of the capital reached 359,827 before the end of the year.

On the orders of Warsaw District Governor, Ludwig Fischer, the ghetto wall construction started on April 1, 1940, circling the area of Warsaw inhabited predominantly by Jews. The work was supervised by the Warsaw Judenrat. The Nazi authorities expelled 113,000 ethnic Poles from the neighbourhood, and ordered the relocation of 138,000 Warsaw Jews from the suburbs into the city center. On October 16, 1940, the creation of the ghetto was announced by the German governor-general, Hans Frank. The initial population of the ghetto was 450,000 confined to an area of 307 hectares (760 acres). Before the Holocaust began the number of Jews imprisoned there was between 375,000 and 400,000 (about 30% of the general population of the capital). The area of the ghetto constituted only about 2.4% of the overall metropolitan area.

The Germans closed the Warsaw Ghetto to the outside world on November 15, 1940. The wall around it was 3 m (9.8 ft) high and topped with barbed wire. Escapees were shot on sight. German policemen from Battalion 61 used to hold victory parties on the days when a large number of prisoners were shot at the ghetto fence. The borders of the ghetto changed and its overall area was gradually reduced, as the captive population was decreased by outbreaks of infectious diseases, mass hunger, and regular executions.

The ghetto was divided in two along Chłodna Street Ulica Chłodna w Warszawie [pl], which was excluded from it, due to its local importance at that time (as one of Warsaw's east–west thoroughfares). The area south-east of Chłodna was known as the "Small Ghetto", while the area north of it became known as the "Large Ghetto". The two zones were connected at an intersection of Chłodna with Żelazna Street, where a special gate was built. In January 1942, the gate was removed and a wooden footbridge was built over it, which became one of the postwar symbols of the Holocaust in occupied Poland.

The first commissioner of the Warsaw Ghetto, appointed by Fischer, was SA-Standartenführer Waldemar Schön, who also supervised the initial Jewish relocations in 1940. He was an attritionist best known for orchestrating an "artificial famine" (künstliche Hungersnot) in January 1941. Schön had eliminated virtually all food supplies to the ghetto causing an uproar among the SS upper echelon. He was relieved of his duties by Frank himself in March 1941 and replaced by Kommissar Heinz Auerswald, a "productionist" who served until November 1942. Like in all Nazi ghettos across occupied Poland, the Germans ascribed the internal administration to a Judenrat Council of the Jews, led by an "Ältester" (the Eldest). In Warsaw, this role was relegated to Adam Czerniaków, who chose a policy of collaboration with the Nazis in the hope of saving lives. Adam Czerniaków confided his harrowing experience in nine diaries. In July 1942, when the Germans ordered him to increase the contingent of people to be deported, he took his own life.