Żyźniewo [ʐɨʑˈɲɛvɔ] is a village in the administrative district of Gmina Troszyn, within Ostrołęka County, Masovian Voivodeship, in east-central Poland. It lies approximately 10 kilometres (6 mi) east of Troszyn, 21 km (13 mi) east of Ostrołęka, and 111 km (69 mi) north-east of Warsaw.