Although the early rulers, from Arnulf I onwards, were sometime referred to as margraves or marquesses, this alternate title largely fell out of use by the 12th century. Since then the rulers of Flanders have only been referred to as counts.
Charles V proclaimed the Pragmatic Sanction of 1549 eternally uniting Flanders with the other lordships of the Low Countries in a personal union. When the Habsburg empire was divided among the heirs of Charles V, the Low Countries, including Flanders, went to Philip II of Spain, of the Spanish branch of the House of Habsburg.
Philip III (r. 1556-1598), son of Charles III, also King of Spain
Philip IV (r. 1621-1665), grandson of Philip III, also King of Spain
Charles IV (r. 1665-1700), son of Philip IV, also King of Spain
Between 1706 and 1714 Flanders was invaded by the English and the Dutch during the War of the Spanish Succession. The fief was claimed by the House of Habsburg and the House of Bourbon. In 1713, the Treaty of Utrecht settled the succession and the County of Flanders went to the Austrian branch of the House of Habsburg.
Charles V (r. 1714-1740), great grandson of Philip III, also Holy Roman Emperor (elect)
Joseph I (r. 1780-1790), son of Maria Theresa and Francis I, also Holy Roman Emperor
Leopold (r. 1790-1792), son of Maria Theresa and Francis I, also Holy Roman Emperor
Francis II (r. 1792-1835), son of Leopold II, also Holy Roman Emperor
The title was factually abolished in the aftermath of the French revolution and the annexation of Flanders by France in 1795. Although, the title remained officially claimed by the descendants of Leopold II until the reign of Karl I, Emperor of the Holy Roman Empire.