Mrówczy Zamek [ˈmruft͡ʂɨ ˈzamɛk] is a settlement in the administrative district of Gmina Szemud, within Wejherowo County, Pomeranian Voivodeship, in northern Poland. It lies approximately 8 kilometres (5 mi) east of Szemud, 17 km (11 mi) south of Wejherowo, and 22 km (14 mi) north-west of the regional capital Gdańsk.

For details of the history of the region, see History of Pomerania.