Biebrza National Park (Polish: Biebrzanski Park Narodowy) is a national park in Podlaskie Voivodship, northeastern Poland, situated along the Biebrza River.
The northeastern boundary of the park is near the Belarus border.The Narew River and its confluence with the Biebrza River form the southern boundary.
Its total area is 592.23 km2 (228.66 sq mi), of which forests cover 155.47 km², fields and meadows covering 181.82 km² and the famous Biebrza River Marshes with an area of 254.94 km².
The largest of Poland’s 23 National Parks, the Biebrza National Park was created on September 9, 1993. The park's headquarters are in Osowiec-Twierdza, in the grounds of the historic Osowiec Fortress, near Goniadz.

Marshes are the most precious part of the park.
Biebrza National Park protects vast and relatively untouched fenlands with a unique variety of several communities of plants, rare wetland birds and mammals such as Elk, Wolf, Lynx, Roe Deer, Red Deer, Badger, Stoat, Otter, Beaver and other animals.
The Biebrza wetlands as well as the Narew River valleys are very important centres for birds’ nesting, feeding and resting.
The Biebrza valley supports a unique group of bird species in Europe. About 270 species have been observed here so far, including 181 breeding birds.
Among 56 species recorded in Polish Red Data Book of Animals (1992), 17 breed in the Park, e.g.: Spotted Eagle Aquila clanga, Great Snipe Gallinago media, Black Tern Chlidonias niger, Aquatic warbler Acrocephalus paludicola.
For some waterfowl species, Biebrza marshes are among the last refuges for the survival of their population in Central Europe. For many groups of animals, there are only sporadic data.
So far 48 mammal species, 13 amphibian species, 5 species of reptiles, 36 species of fish and Ukrainian lamprey, over 750 species of moths and butterflies, 500 species of battles, 11 species of bats, 42 species of caddis-fly, about 450 species of spiders and 19 of leeches have been recorded.

Unique in Europe for its marshes and peatlands, as well as its highly diversified fauna, especially birds - the Park was designated in 1995 as a wetland site of global significance and is under the protection of the RAMSAR Convention.
The most important area of 3 936 ha is under strict protection including the Czerwone Bagno or Red Bog at the Grzedy Forest District.