Mierzączka [mjɛˈʐɔnt͡ʂka] is a village in the administrative district of Gmina Górzno, within Garwolin County, Masovian Voivodeship, in east-central Poland. It lies approximately 3 kilometres (2 mi) north-west of Górzno, 6 km (4 mi) south-east of Garwolin, and 62 km (39 mi) south-east of Warsaw.