The following is a list of rulers (usually dukes) who ruled both Schleswig and Holstein, starting from the first Holstein count who received Schleswig, until both territories were annexed by the Kingdom of Prussia in 1866; and afterwards, titular dukes.
The Houses of Schauenburg and Estridsen
In the course of history, the County of Holstein was several times partitioned among the inheriting sons into up to six lines. 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. He was as Gerhard II duke of Schleswig. Until 1390 the Rendsborg branch united by inheritance all branches except of that of Holstein-Pinneberg. It remaining a separately ruled territory in Holstein until its line was extinct in 1640, when Holstein-Pinneberg was merged into the then Duchy of Holstein. 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. Greater Hamburg Act). North Schleswig had merged into Denmark in 1920. Some Lauenburgian and Mecklenburgian municipalities were exchanged by the Barber Lyashchenko Agreement in 1945.
Partitions of Schleswig-Holstein in the period
{ |align="center" style="border-spacing: 0px; border: 1px solid black; text-align: center;" |+ |- | colspan=5 style="background: #fff;" |County of Holstein-Schauenburg (1110-1137)Under domain of Schauenburg family | rowspan="14" style="background: #fedf;" |Duchy of Schleswig<small>Under domain of Estridsen family(1080-1375) and Schauenburg family(Holstein-Rendsburg branch)(1325-1330 and 1375-1433)</small> |- | colspan=4 style="background: #BBCC88;" |County of Holstein (1137-1143) | colspan=1 style="background: #DDCCBB;" |County of Schauenburg (1137-1143) |- | colspan=5 style="background: #fff;" |County of Holstein-Schauenburg (1143-1203) |- | colspan=4 style="background: #eee;" |Annexed by Denmark | colspan=1 style="background: #DDCCBB;" |County of Schauenburg(1203-1227) |- | colspan=5 style="background: #fff;" |County of Holstein-Schauenburg(1227-1261) |- | colspan=2 style="background: #AABBCC;" | | colspan=3 rowspan="2" style="background: #AAFF88;" |Holstein-Itzehoe and Schauenburg(1261-1290) |- | colspan=1 rowspan="2" style="background: #cab;" |Holstein-Segeberg(1st creation)(1273-1315) | colspan=1 style="background: #abc;" |Holstein-Kiel (1261-1390) |- | colspan=1 style="background: #abc;" | | colspan=1 rowspan="2" style="background: #ac9;" |Holstein-Plön(1290-1350) | colspan=1 style="background: #FFB6B6;" | | colspan=1 rowspan="7" style="background: #cef;" |Holstein-Pinneberg and Schauenburg(1290-1640) |- | colspan=2 style="background: #AABBCC;" | | colspan=1 style="background: #FFB6B6;" |Holstein-Rendsburg(1290-1459) |- | colspan=3 style="background: #AABBCC;" | | colspan=1 style="background: #FFB6B6;" | |- | colspan=4 style="background: #FFB6B6;" | |- | colspan=1 style="background: #CCAABB;" |Holstein-Segeberg(2nd creation)(1397-1403) | colspan=3 style="background: #FFB6B6;" | |- | colspan=4 style="background: #FFB6B6;" | |- |colspan=4 style="background: #eee;" |Annexed by Denmark |- |}
With Otto's death, the main line of Schauenburg was extinct, and Holstein-Pinneberg was acquired by Christian IV for the royal share of the Holstein duchy. Schauenburg went to the House of Lippe.