Polesia, Polissia, Polesie, or Polesye is a natural and historical region in Eastern Europe, including part of Eastern Poland, the Belarus–Ukraine border region.
One of the largest forest areas on the continent, Polesia is located in the southwestern part of the Eastern-European Lowland, the Polesian Lowland. On the western side, Polesia originates at the crossing of the Bug River valley in Poland and the Pripyat River valley of Western Ukraine. The swampy areas of central Polesia are known as the Pinsk Marshes (after the major local city of Pinsk). Large parts of the region were contaminated after the Chernobyl disaster and the region now includes the Chernobyl Exclusion Zone and Polesie State Radioecological Reserve, named after the region.
The names Polesia/Polissia/Polesye, etc. may reflect the Slavic root les 'forest', and the Slavic prefix po- 'on, in, along'. Inhabitants of Polesia are called Polishchuks.
In ancient times, the areas of today's western and west-central Polesia were inhabited by the people of the Milograd culture, the Neuri.
In the late Middle Ages Polesia became part of the Grand Duchy of Lithuania, following it into the Polish–Lithuanian Commonwealth (1569). Polesia was largely part of Poland from 1921 to 1939, when the country's largest provinces bore that name.
Polesia has rarely been a separate administrative unit. However, there was a Polesie Voivodeship during the Second Polish Republic, as well as a Polesia Voblast in Byelorussian SSR. From 1931 to 1944, it was explicitly mentioned as constituent part of the short-lived (Byzantine Rite) Ukrainian Catholic Apostolic Exarchate of Volhynia, Polesia and Pidliashia. Since the end of World War II, the region of Polesie or Polesia has encompassed areas in eastern Poland, southern Belarus, northwestern Ukraine, and southwestern Russia.
Polesia is a marshy region lining the Pripyat River (Pripyat Marshes) in Southern Belarus (Brest, Pinsk, Kalinkavichy, Gomel), Northern Ukraine (in the Volyn, Rivne, Zhytomyr, Kyiv and Chernihiv Oblasts), and partly in Poland (Lublin) and Russia (Bryansk).