The national flag of Estonia (Estonian: Eesti riigilipp) is a tricolour featuring three equal horizontal bands of blue (top), black, and white. The normal size is 105 by 165 centimetres (41 in × 65 in). In Estonian it is colloquially called the "sinimustvalge" (lit. '"blue-black-white"'), after the colours of the bands.

The tricolour was already in wide use as the symbol of Estonia and Estonians when the country gained independence in 1918. Formally, it obtained the status of the official national flag on 16 July 1922. The tricolour was used as the national flag until June 1940 when the Soviet Union invaded and occupied Estonia. After the annexation of Estonia by the Soviet Union in August 1940, the use of the national tricolour and its blue, black and white colour combination was banned and punishable by law in the Soviet Union. The national flag was from 1940 until 1991 continuously used by the Estonian government-in-exile, diplomatic service, and the Estonian diaspora around the world.

In October 1988, the usage of the blue-black-white flag was officially permitted again by Estonian authorities. On the evening of 23 February 1989 the Soviet flag was taken down permanently from the tower of Pikk Hermann of the Toompea Castle. It was replaced with the national blue-black-white flag on the next morning, 24 February, upon the 70th anniversary of the Estonian Declaration of Independence (1918). The national flag was officially re-adopted by the Estonian authorities 7 August 1990, one year before the nation's full restoration of independence.