Popielżyn Dolny [pɔˈpjɛlʐɨn ˈdɔlnɨ] is a village in the administrative district of Gmina Nowe Miasto, within Płońsk County, Masovian Voivodeship, in east-central Poland. It lies approximately 17 kilometres (11 mi) east of Płońsk and 50 km (31 mi) north-west of Warsaw.