Białowieza (byälôvyĕˈzhä) [key], Rus. Byelovezhskaya Pushcha, large forest, c.450 sq mi (1,170 sq km), E Poland and W Belarus. The last great first-growth forest of Europe, its varied trees (predominantly pines) shelter many animals, including boar, deer, European bison, and tarpan horse. It was a favorite hunting ground of Polish kings. It passed to Prussia in 1795, was annexed by Russia in 1807, but was restored to Poland in 1921. In 1939, however, the forest was incorporated into the USSR. After World War II nearly half of the region was returned to Poland. Today both sections of the forest have animal preserves. The first Polish national park was established in the center of the forest in 1921.