Greater Poland or Great Poland, Polish Wielkopolska (German: Großpolen, Latin: Polonia Maior) is a historical region of west-central Poland. Its chief city is Poznań. Administratively, most of the region now forms Greater Poland Voivodeship (Polish: województwo wielkopolskie), although some parts lie in Lubusz, Kuyavian-Pomeranian and Łódź Voivodeships.
Greater Poland was the core of the early medieval Polish state. It is often termed "the cradle of Poland", and at times has simply been called "Poland" (Latin Polonia). The name is first mentioned in the Latin form Polonia Maior in 1257, and in Polish ("w Wielkej Polszcze") in 1449. The region's name may be construed as referring to old Poland, as opposed to the new Poland, Lesser Poland (Polish: Małopolska; Latin: Polonia Minor), a region in southern Poland with its capital at Kraków. In 1796 it was renamed Grand Duchy of Posen and in the 19th century mostly became part of the Province of Posen, within Prussia, later part of the German Empire.
Greater Poland comprises much of the area drained by the Warta River and its tributaries, including the Noteć River. There are two major geographic regions: a lake district in the north, characterized by post-glacial lakes and hills, and a rather flat plain in the south.
An area of 75.84km2 of forest and lakeland south of Poznań is designated the Wielkopolska National Park (Wielkopolski Park Narodowy), established in 1957.