From the Wikipedia page 
Region Zealand (Danish: Region Sjælland) is the southernmost administrative region of Denmark, established on January 1, 2007 as part of the 2007 Danish Municipal Reform, which abolished the traditional counties ("amter") and set up five larger regions. Zealand Region has 17 municipalities.
Zealand Region consists of the former counties of Roskilde, Storstrøm, and Vestsjælland.
The region is named after the island of Sjælland (Zealand), which it shares with the neighbouring Danish Capital Region. Region Zealand (Region Sjælland) also includes the adjacent islands of Lolland, Falster, and Møn.