The area of modern Belarus was settled by East Slavic peoples before 800 A.D. It was ruled by Kiev from the 9th to the 12th century, and thereafter splintered into separate principalities. Early in the 14th century, it became part of the Grand Duchy of Lithuania, which merged with Poland in 1569. Late in the 18th century, Russia acquired the region through the three partitions of Poland—1773, 1793, and 1795.

The region was devastated by the Napoleonic invasion of 1812 and again in World War I. After the war, Poland and Russia fought for control of the region. By the Treaty of Riga, 1921, Poland acquired the western portion of the region while Russia retained the eastern portion.

In 1922 the eastern portion was made a union republic of the Soviet Union as the Byelorussian Soviet Socialist Republic. The entire region was occupied by Germany during most of World War II. After the war, the Polish portion of the region was incorporated into the Byelorussian S.S.R. As a concession by the Western Allies to secure Soviet cooperation in establishing the United Nations, the Byelorussian S.S.R., although part of the Soviet Union, was admitted to the organization as a charter member with a separate vote.

During 1990–91, rising nationalism throughout the union republics gradually eroded the authority of the Soviet central government. In 1991 the Byelorussian S.S.R. declared itself independent and changed its name to Republic of Belarus. After the Soviet Union collapsed in 1991, Belarus achieved independence. Also that year, Belarus joined the Commonwealth of Independent States. In 1992, in an international agreement, Belarus promised to relinquish its nuclear weapons. Belarus and Russia signed an agreement in 1996 that established close political and economic ties.

Aleksandr Lukashenko, elected president in 1994, successfully pushed through a referendum for a new constitution in 1996 that expanded his power and extended his presidential term to 2001. Lukashenko was reelected in 2001 and 2006 despite continuous accusations of vote fraud and undemocratic voting policies. Opponents accused Lukashenko of setting up a dictatorship and limiting the people's freedoms.