Kostrogaj [kɔsˈtrɔɡai̯] is a village in the administrative district of Gmina Radzanowo, within Płock County, Masovian Voivodeship, in east-central Poland. It lies approximately 11 kilometres (7 mi) west of Radzanowo, 4 km (2 mi) north-east of Płock, and 94 km (58 mi) north-west of Warsaw.