Książ Wielkopolski (Polish pronunciation: [ˈkɕɔ̃ʐ vjɛlkɔˈpɔlskʲi]; German: Xions, 1940–43 Tiefenbach, 1943–45 Schonz) is a town in Śrem County, Poland, with 2,738 inhabitants (2010).

The town was first mentioned in a bull of Pope Celestine III in 1193, when it was part of Piast-ruled Poland. In 1273 it was mentioned as a seat of a castellany. It was granted town rights between 1398 and 1416. Książ was a private town of Polish nobility, administratively located in the Kościan County in the Poznań Voivodeship in the Greater Poland Province of the Kingdom of Poland.

Following the joint German-Soviet invasion of Poland, which started World War II in September 1939, the town was occupied by Germany until 1945 and local Poles were subjected to various crimes. On October 20, 1939, the German Einsatzgruppe VI carried out a public execution of 17 Poles at the main square as part of the Intelligenzaktion. Among the victims were a bank director, teacher, merchant, forester, military officer, landowners and mayor of the nearby town of Dolsk. It was one of many massacres of Poles committed by Germany on October 20–23 across the region in attempt to pacify and terrorize the Polish population. The first expulsions of Poles were carried out by Germany in winter of 1939–1940. Under German occupation the town's name was changed to Tiefenbach and then Schonz in attempt to erase traces of Polish origin.

Historical population

Year Pop. ±% 1843 1,087 —     1871 1,019 −6.3% 1880 998 −2.1% 1890 948 −5.0% 1900 918 −3.2% 1910 874 −4.8%	Year Pop. ±% 1921 913 +4.5% 1931 928 +1.6% 1939 1,800 +94.0% 1950 1,597 −11.3% 1960 1,744 +9.2% 2010 2,738 +57.0%
Source:

The local football club is Pogoń Książ Wielkopolski. It competes in the lower leagues.

• Heinrich Graetz (1817–1891), historian, wrote a history of the Jewish people from a Jewish perspective.