Ostrołęka County (Polish: powiat ostrołęcki) is a unit of territorial administration and local government (powiat) in Masovian Voivodeship, east-central Poland. It came into being on January 1, 1999, as a result of the Polish local government reforms passed in 1998. Its administrative seat is the city of Ostrołęka, although the city is not part of the county (it constitutes a separate city county). The only town in Ostrołęka County is Myszyniec, which lies 38 km (24 mi) north of Ostrołęka.