Mętna [ˈmɛntna] is a village in the administrative district of Gmina Mielnik, within Siemiatycze County, Podlaskie Voivodeship, in north-eastern Poland, close to the border with Belarus. It lies approximately 6 kilometres (4 mi) east of Mielnik, 21 km (13 mi) south-east of Siemiatycze, and 86 km (53 mi) south of the regional capital Białystok.