The Radomka is a river in central Poland and a left tributary of the Vistula. It has a length of 98 km and a basin area of over 2000 km² (all in Poland). The river has its source in forests 4 km south from Przysucha, at the height of 310 meters above sea level. There is a retention reservoir, built in the valley of the Radomka in Domaniów, which has the largest surface area of any lakes in Mazowsze Voivodeship (5 – 7 km²).