The national flag of Estonia (Eesti lipp) is a tricolour featuring three equal horizontal bands of blue at the top, black in the middle, and white at the bottom. The flag is called sinimustvalge (lit. 'blue-black-white') in Estonian.

The tricolour was already in wide use as the symbol of the nation, when the Republic of Estonia became an independent country in 1918. Formally, the tricolour became the national flag by the decision of the Estonian government on 21 November 1918, and the parliament later reconfirmed the flag's official status with a law in 1922.

During World War II, soon after the Soviet army had invaded and occupied Estonia in June 1940, the new Stalinist occupation regime banned the Estonian flag, and its use as well as any use of its blue, black and white colour combination became punishable by laws of the Soviet Union. The Estonian flag was from 1940 until 1991 continuously used by the Estonian government-in-exile, diplomatic service, and the diaspora of Estonian refugees around the world. Wikipedia