Kostrzynek [kɔsˈtʂɨnɛk] is a village in the administrative district of Gmina Wysoka, within Piła County, Greater Poland Voivodeship, in west-central Poland. It lies approximately 8 kilometres (5 mi) west of Wysoka, 18 km (11 mi) east of Piła, and 88 km (55 mi) north of the regional capital Poznań.

When this area was part of Prussia, it was known as Künstrinchen or Küstrinchen.