The Principality of Nitra, also known as the Duchy of Nitra, was a West Slavic polity encompassing a group of settlements that developed in the 9th century around Nitra, in present-day Slovakia. Its history remains uncertain because of a lack of contemporary sources. The territory's status is subject to scholarly debate: some modern historians describe it as an independent polity that was annexed either around 833 or 870 by the Principality of Moravia, while others say that it was under the influence of the neighbouring West Slavs from Moravia from its inception.

The West Slavs are Slavic peoples who speak the West Slavic languages. They separated from the common Slavic group around the 7th century, and established independent polities in Central Europe by the 8th to 9th centuries. The West Slavic languages diversified into their historically attested forms over the 10th to 14th centuries.