Żnin [ʐnin] (German: Dietfurt) is a small town in Poland with a population of 14,558 (June 2005). It is in the Kuyavian-Pomeranian Voivodeship (previously Bydgoszcz Voivodeship) and is the capital of Żnin County. The town is situated in the historic land of Pałuki and the Gniezno Lake Area on the river Gąsawka.

The name originates from the Polish word "żnieja", meaning harvest or a harvester. During World War II, Żnin's name was "Dietfurt".

The area was known in Roman times, especially the nearby fortification of Biskupin, a Lusatian culture site known as the "Polish Pompeii". Biskupin was an early Iron Age Hallstatt C fortified settlement of about 800-1000 people in the Warta River valley circa 800-650 and 650-475 BC.

By 1030 the area was included within the Archbishopric of Gniezno. The first mention of Żnin is in the Gniezno papal bull issued on 7 July 1136 by Pope Innocent II. The pope granted Archbishop Jacob of Żnin 29 villages in Pałuki and the town of Żnin, which also became property of the Roman Catholic Church.