Białowieża Forest is a large forest complex on the border between Poland and Belarus. It is one of the last and the largest remaining part of the immense primeval forest that once stretched across the European Plain. The forest is home to more than 800 European bisons, Europe's heaviest land animal. UNESCO's Man and the Biosphere Programme designated the Polish Biosphere Reserve Białowieża in 1976 and the Belarusian Biosphere Reserve Biełavieskaja pušča in 1993.

In 2015, the Belarusian Biosphere Reserve spanned 216,200 ha (2,162 km; 835 sq mi), subdivided into transition, buffer and core zones. The forest has been designated a UNESCO World Heritage Site and an EU Natura 2000 Special Area of Conservation. The World Heritage Committee, through its decision of June 2014, approved the extension of the UNESCO World Heritage site "Belovezhskaya Pushcha / Białowieża Forest, Belarus, Poland", which became "Białowieża Forest, Belarus, Poland". It straddles the border between Podlachia historical region in Poland and Brest and Grodno Oblasts in Belarus, and is 62 kilometres (39 miles) southeast of Białystok, Poland and 70 kilometres (43 miles) north of Brest, Belarus. The Białowieża Forest World Heritage site covers a total area of 141,885 ha (1,418.85 km; 547.82 sq mi). Since the border between the two countries runs through the forest, there is a border crossing available for hikers and cyclists.

The Białowieża Forest takes its name from the Polish village of Białowieża, which is located in the middle of the forest and was probably one of the first human settlements in the area. Białowieża means "White Tower" in Polish. The name stems from the white wooden hunting-manor established in the village by Władysław II Jagiełło, the Grand Duke of Lithuania and later King of Poland who enjoyed going on hunting trips in the forest, which was then part of the Grand Duchy of Lithuania. The modern Belarusian name for the forest is Biełaviežskaja pušča (Белавежская пушча), although both the Belarusian authorities and UNESCO use the official Russian name Belovezhskaya pushcha (Беловежская пуща) from before the 1991 dissolution of the Soviet Union.