Mierzynówka [mjɛʐɨˈnufka] is a village in the administrative district of Gmina Grodzisk, within Siemiatycze County, Podlaskie Voivodeship, in north-eastern Poland. It lies approximately 2 kilometres (1 mi) east of Grodzisk, 20 km (12 mi) north of Siemiatycze, and 65 km (40 mi) south-west of the regional capital Białystok.