Grabnik [ˈɡrabnik] is a village in the administrative district of Gmina Olszewo-Borki, within Ostrołęka County, Masovian Voivodeship, in east-central Poland. It lies approximately 9 kilometres (6 mi) north-west of Olszewo-Borki, 12 km (7 mi) west of Ostrołęka, and 102 km (63 mi) north of Warsaw.