Holstein-Gottorp is the historiographical name, as well as contemporary shorthand name, for the parts of the duchies of Schleswig and Holstein, also known as Ducal Holstein, that were ruled by the dukes of Schleswig-Holstein-Gottorp, a side branch of the elder Danish line of the German House of Oldenburg. Other parts of the duchies were ruled by the kings of Denmark.

The Duchy of Schleswig was a duchy in Southern Jutland covering the area between about 60 km north and 70 km (45 mi) south of the current border between Germany and Denmark. The territory has been divided between the two countries since 1920, with Northern Schleswig in Denmark and Southern Schleswig in Germany. The region is also called Sleswick in English.