During most of its history, Poland was a multiethnic society that included substantial numbers of Belarusians (prior to 1992 known as Belorussians), Germans, Jews, and Ukrainians. This ethnic diversity was reduced sharply by World War II and the migrations that followed it. The Jewish population, which in the interwar period was over 10 percent of Poland's total and over 30 percent of Warsaw's, was reduced by about 3 million in the Holocaust. Postwar resettlement and adjustment of borders sent about 2 million Germans from Polish territory westward and awarded the Polish territory inhabited by 500,000 Ukrainians, Belarusians, and Lithuanians to the Soviet Union. These multiethnic émigrés were replaced by an estimated 3 million ethnic Poles repatriated from the Soviet Union and by thousands of others who returned from emigration or combat in the West. (Poland's communist governments, which consistently emphasized ethnic homogeneity, had not differentiated ethnic groups in official census statistics.) As a result of this process, in 1990 an estimated 98 percent of Poland's population was ethnically Polish.

Data as of October 1992