Mrocza (Polish pronunciation: [ˈmrɔt͡ʂa]; German: Mrotschen, 1939-1942: Schönhausen, 1942-1945: Immenheim) is a town in Nakło County, Kuyavian-Pomeranian Voivodeship, northern Poland,[2] with 4,368 inhabitants (2010).

It was a private town, administratively located in the Nakło County in the Kalisz Voivodeship in the Greater Poland Province.

[3] Following the joint German-Soviet invasion of Poland, which started World War II in September 1939, the town was invaded and then occupied by Germany.

In October–November 1939, as part of the Intelligenzaktion, the German gendarmerie and Selbstschutz carried out mass arrests of local Poles, including the town's mayor.

Tarpan Mrocza sports club is based in the town, with football, weightlifting and duplicate bridge sections.