Silesia,a historic region of east-central Europe. It occupies the upper valley of the Oder River and is bounded on the south and west by the Sudeten Mountains. All of lower Silesia (the northern two-thirds of the region) and most of upper Silesia (the southern part) are now part of southwestern Poland; a small section of upper Silesia lies in the Czech Republic. Upper Silesia is primarily industrial and contains some of Europe's richest coalfields; lower Silesia is primarily agricultural. Wroclaw and Katowice are the area's chief cities.

Slavic tribes had settled in Silesia by the sixth century A.D. In the llth century the region was conquered by Poland, but Polish rule weakened and in the 14th century Silesia passed to Bohemia. Silesia came under control of Austria in 1526.

In 1740 Prussia invaded Silesia, initiating the first of three Silesian Wars with Austria. The first two wars were part of the War of the Austrian Succession. The first war ended in 1742 when Silesia was ceded to Prussia. Austria failed to recover the territory in the second war (1744–45) and the third (1756–63), which was part of a more general conflict, the Seven Years' War.

When the German Empire was formed in 1871, Silesia, as part of Prussia, was incorporated into it. After World War I small sections of upper Silesia went to Poland and Czechoslovakia. After World War II, changes in boundaries placed the German portions of Silesia in Poland.