horizontally striped red-green national flag with a vertical stripe of red and white at the hoist. Its width-to-length ratio is 1 to 2.

The Slavic (Slav) peoples of what is now Belarus were in the past ruled by Prussia, Poland, Lithuania, and Russia. Consequently no distinctive national symbols were developed until the 20th century, when for the first time Belarus became independent. With the breakup of the Russian Empire near the end of World War I, a Belarusian state existed briefly. Its first flag was plain white, reflecting the nation's name, which means “White Russia.” Later a red horizontal stripe was added through the centre of the flag. These colours were derived from the traditional coat of arms (arms, coat of) used by Belarus under Lithuanian rule, a red shield with a white horse and knight.

Communist forces displayed a plain red flag in Belarus, although various inscriptions in gold or white were later added. The Belorussian Soviet Socialist Republic created a distinctive flag in 1951 that had unequal horizontal stripes of red (for communism) and light green (for the fields and forests of the country); the golden hammer, sickle, and star of communism appeared on the red stripe. In addition a distinctive vertical stripe was added at the hoist: this was red with a white embroidery pattern typical of designs found on peasant blouses and shirts. The Belorussian flag was thus the first flag design in the Soviet Union (Union of Soviet Socialist Republics) to include national ornamentation.