Brzezienko [bʐɛˈʑɛnkɔ] is a village in the administrative district of Gmina Wąsewo, within Ostrów Mazowiecka County, Masovian Voivodeship, in east-central Poland. It lies approximately 21 kilometres (13 mi) north-west of Ostrów Mazowiecka and 86 km (53 mi) north-east of Warsaw.