Greater Poland, often known by its Polish name Wielkopolska [vʲɛlkɔˈpɔlska] (German:Großpolen; Latin: Polonia Maior) is a historical region of west-central Poland. Its chief city is Poznań.

The boundaries of Greater Poland have varied somewhat throughout history. Since the Middle Ages the proper (właściwa) or exact/strict (ścisła) Wielkopolska (often referred to as ziemia, that means land) included the Poznań and Kalisz voivodeships. In the wider sense (as dzielnica, i.e. region) it encompassed also Sieradz, Łęczyca, Brześć Kujawski and Inowrocław voivodeships (more eastward). One another meaning (as province) included also Mazovia and Royal Prussia. After the Partitions of Poland, Greater Poland was often identified with the Grand Duchy of Posen. The region in the proper sense roughly coincides with the present-day Greater Poland Voivodeship (Polish:województwo wielkopolskie).