Ulasek [uˈlasɛk] is a village in the administrative district of Gmina Wąsewo, within Ostrów Mazowiecka County, Masovian Voivodeship, in east-central Poland. It lies approximately 4 kilometres (2 mi) south of Wąsewo, 18 km (11 mi) west of Ostrów Mazowiecka, and 83 km (52 mi) north-east of Warsaw.