Kuyavia (Polish: Kujawy; Latin: Cuiavia), also referred to as Cujavia, is a historical region in north-central Poland, situated on the left bank of Vistula, as well as east from Noteć River and Lake Gopło. It is divided into three traditional parts: north-western (with the capital in Bydgoszcz, ethnographically distinct^{[citation needed]}), central (the capital in Inowrocław or Kruszwica), and south-eastern (the capital in Włocławek or Brześć Kujawski).

The name Kuyavia first appeared in written sources in the 1136 Bull of Gniezno (Polish: Bulla Gnieźnieńska, Latin: Ex commisso nobis) issued by Pope Innocent II, and was then mentioned in many documents from medieval times. It is also mentioned in the chronicles of Wincenty Kadłubek.

In the north, Kuyavia borders with the historic regions of Gdańsk Pomerania (Pomerelia) and Chełmno Land, in the west with proper (exact) Greater Poland, in the south with Łęczyca Land and in the east with Masovia and Dobrzyń Land. The borders of Kuyavia stretch out on the left bank of Vistula River: from the mouth of Skrwa Lewa in the south-east, almost to the mouth of the Wda River to the north. The borders of Kuyavia spread out to the west from Koronowo and Nakło to the Noteć River where they turn south-west, cross Trląg Lake, and on to Strzelneński Forest, reaching Skulski Lake and the upper Noteć River. The borders also enclose Brdowski Lake, Przedecz and Lubień Kujawski through the Skrwa Lewa, ending at the Vistula River.

Also the southern part of Toruń (Podgórz) lies in the historical region. Some ethnographers and historians, for example Oskar Kolberg and Zygmunt Gloger, count the lands of Dobrzyń and Chełmno north-east of the Vistula as parts of the Kuyavia region.^{[citation needed]}

The Kuyavian lowlands have an average elevation of 100–130 meters above sea level. It is post-glacial landscape, slightly undulating, in some places there are moraine hills and sandy gravel embankments. In deep dykes and depressions there are approximately 600 lakes larger than 1 km². Under the glacial formations there are layers of rock-salt and potassium, and under Tertiary Period sediments there is lignite and ceramic clay. In Kuyavia there are black fertile soils, thanks to which Kuyavia is called "the granary of Poland".

Kuyavia has been historically a rich, densely populated and decentralised region of the Polish state, one of the smaller yet distinct provinces of Poland. Kruszwica was the political centre of the early Goplan tribe, identified with the peoples of Kuyavia. In this area, Kruszwica was also the earliest episcopal see, created on territory split off from archdiocese of Gniezno and as a replacement for the dissolved diocese of Kołobrzeg. In the middle of the 12th century, its seat was moved to Włocławek. This diocese governed the lands of both Kuyavia and Pomerania (in 1243, the Dioecese of Chełmno was founded for Teutonic Chełmno Land). So would remain up until Polish partitions, when episcopate borders were changed and Kuyavia was divided between dioceses of Gniezno (for the Prussian part) and of Włocławek (for the Russian part). Today in Kuyavia both Włocławek and Bydgoszcz have their own bishoprics.

The first independent Duchy of Kuyavia was created in 1230 with the capital in Inowrocław. It would be defragmented often into smaller principalities with its seats also in Bydgoszcz (with Wyszogród), Gniewkowo and Brześć Kujawski. In the late 14th century, the administrative division of the unified Polish kingdom was introduced; in Kuyavia, the residency of the Voivode governors was both Inowrocław and Brześć Kujawski, with Radziejów serving as the seat of the shared regional Sejmik council of the two voivodeships.

Bydgoszcz has been the main economic centre of Kuyavia since the Polish Golden Age. First it was a strategic point as a defensive castle near the Polish border with the hostile Teutonic Order. Soon it became the largest urban centre of Kuyavia and a significant trade hub, specifically serving as an intermediary in trade with Gdańsk, whose importance extended beyond the Kuyavian region. Its economic role involved linking the Baltic port with the hinterlands of the Brda and Noteć rivers as well as sections of Vistula and Warta.