Sienno [ˈɕɛnnɔ] is a village in the administrative district of Gmina Ośno Lubuskie, within Słubice County, Lubusz Voivodeship, in western Poland. It lies approximately 7 kilometres (4 mi) west of Ośno Lubuskie, 20 km (12 mi) north-east of Słubice, 44 km (27 mi) south-west of Gorzów Wielkopolski, and 77 km (48 mi) north-west of Zielona Góra.