The House of Hesse is a European dynasty, directly descended from the House of Brabant, and ruled the region of Hesse, with one branch as prince electors until 1866, and another branch as grand dukes until 1918.
The origins of the House of Hesse begin with the marriage of Sophie of Thuringia, daughter of Louis IV, Landgrave of Thuringia and Elizabeth of Hungary with Henry II, Duke of Brabant from the House of Reginar. Sophie was the heiress of Hesse which she passed on to her son, Henry upon her retention of the territory following her partial victory in the War of the Thuringian Succession in which she was one of the belligerents.
Originally the western part of the Landgraviate of Thuringia, in the mid 13th century it was inherited by the younger son of Henry II, Duke of Brabant, and became a distinct political entity. From the late 16th century it was generally divided into several branches, the most important of which were those of Hesse-Kassel (or Hesse-Cassel) and Hesse-Darmstadt. In the early 19th century the Landgrave of Hesse-Kassel was elevated to Elector of Hesse (1803), while the Landgrave of Hesse-Darmstadt became the Grand Duke of Hesse (1806), later Grand Duke of Hesse and by Rhine. The Electorate of Hesse (Hesse-Kassel) was annexed by Prussia in 1866, while Grand Ducal Hesse (Hesse-Darmstadt) remained a sovereign realm until the end of the German monarchies in 1918.
Donatus, Landgrave of Hesse is the current (February, 2018) head of the house.
The Battenberg family are morganatic descendants in the male-line of the House of Hesse, issuing from the marriage of Prince Alexander of Hesse and by Rhine with Countess Julia Hauke who, along with her children and agnatic descendants, were made princes and princesses of Battenberg and Serene Highnesses. The Battenbergs who later settled in England changed that name to Mountbatten after World War I at the behest of George V, who substituted British peerages for their former German princely title. Those descended from the marriage of Alexander of Battenberg, Prince of Bulgaria, contracted with a commoner after the loss of his throne, were granted the title Count von Hartenau.
Hesse-Kassel and its junior lines were annexed by Prussia in 1866; Hesse-Darmstadt became the People's State of Hesse when the monarchy was abolished in 1918. Hesse-Philippsthal died out in the male line in 1925, Hesse-Darmstadt in 1968. The male-line heirs of Hesse-Kassel and Hesse-Philippsthal-Barchfeld flourish.