Holstein-Glückstadt or
Schleswig-Holstein-Glückstadt is the historiographical name, as well as contemporary shorthand name, for the parts of the duchies of
Schleswig and
Holstein that were ruled by the
Kings of Denmark in their function as dukes of Schleswig and Holstein, thus also known as
Royal Schleswig-Holstein. Other parts of the duchies were ruled by the
Dukes of Schleswig-Holstein-Gottorp. The territories of Holstein-Glückstadt are located in present-day
Denmark and
Germany. The main centre of administration was
Segeberg and from 1648
Glückstadt (founded in 1617) on the River
Elbe.