List of rulers of Schleswig-Holstein

In 1386 King Oluf II of Denmark and his mother-regent, Queen Margaret I, enfeoffed in Nyborg Gerhard VI, Count of Holstein-Rendsborg and his cognatic successors with the Duchy of Schleswig, which had been in the royal family's hands until 1375.

Furthermore, the here mentioned rulers of course only reigned Holstein and Schleswig in their respective territorial composition of the time, thus without states and territories only merged later in what became today's State of Schleswig-Holstein, such as Ditmarsh, conquered and annexed in 1559, Saxe-Lauenburg merged in 1876, Heligoland (British rule 1807–1891), Free and Hanseatic City of Lübeck, Region of Lübeck, together with some Hamburgian exclaves in 1937.

In turn much of the current westerly, northerly and easterly suburbs within Greater Hamburg were ceded from Holstein on 1 April 1937 (Cf.

The Danish monarchs and the Dukes of Holstein-Gottorp listed below ruled both duchies together as to general government, however, collected their revenues in their separate estates.

John II the Elder conveniently called Duke of Schleswig-Holstein-Haderslev produced no issue, so no branch emerged from his side.

Following the defeat of Austria in the Austro-Prussian War in 1866, they were annexed by Prussia and were formed into the new Prussian Province of Schleswig-Holstein, part of Germany since 1870.