The (First) Slovak Republic (Slovak: [Prvá] Slovenská republika), otherwise known as the Slovak State (Slovenský štát), was a partially-recognized client state of Nazi Germany which existed between 14 March 1939 and 4 April 1945. The Slovak part of Czechoslovakia declared independence with German support one day before the German occupation of Bohemia and Moravia. The Slovak Republic controlled the majority of the territory of present-day Slovakia but without its current southern parts, which were ceded by Czechoslovakia to Hungary in 1938. It was the first time in history that Slovakia had been a formally independent state.

A one-party state governed by the far-right Hlinka's Slovak People's Party, the Slovak Republic is primarily known for its collaboration with Nazi Germany, which included sending troops to the invasion of Poland in September 1939 and the invasion of the Soviet Union in 1941. In 1942, the country deported 58,000 Jews (two-thirds of the Slovak Jewish population) to German-occupied Poland, paying Germany 500 Reichsmarks each. After an increase in the activity of anti-Nazi Slovak partisans, Germany invaded Slovakia, triggering a major uprising. The Slovak Republic was abolished after the Soviet occupation in 1945 and its territory was reintegrated into the recreated Third Czechoslovak Republic.

The current Slovak Republic does not consider itself a successor state of the wartime Slovak Republic, instead tracing its lineage to the Czechoslovak government-in-exile. However, some nationalists continue to celebrate 14 March as a day of independence.