Sierpc County (Polish: powiat sierpecki) is a unit of territorial administration and local government (powiat) in Masovian Voivodeship, east-central Poland. It came into being on January 1, 1999, as a result of the Polish local government reforms passed in 1998. Its administrative seat and only town is Sierpc, which lies 117 kilometres (73 mi) north-west of Warsaw. The county covers an area of 852.89 square kilometres (329.3 sq mi). As of 2006 its total population is 53,811, out of which the population of Sierpc is 18,791 and the rural population is 35,020.