Holbæk municipality is a municipality (Danish, kommune) in northeastern Region Sjælland on the island of Zealand (Sjælland) in Denmark. The municipality includes the island of Orø, and covers an area of 583 km², and has a total population of 69,010 (2008). Its mayor for 2010–2013 is Søren Kjærsgaard, a member of the Liberal Party (Venstre) political party. The main town and the site of its municipal council is the city of Holbæk. The town's name originates from a 16th Century guildmaster named Jan Holbæk.