Wierzba [ˈvjɛʐba] (German: Wiersba (1938–45: Beldahnsee)) is a village in the administrative district of Gmina Ruciane-Nida, within Pisz County, Warmian-Masurian Voivodeship, in northern Poland. It lies approximately 15 kilometres (9 mi) north of Ruciane-Nida, 21 km (13 mi) north-west of Pisz, and 74 km (46 mi) east of the regional capital Olsztyn.