

The Count of Flanders was the ruler or sub-ruler of the county of Flanders from the 9th century until the abolition of the position by the French revolutionaries in 1790.
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.
The Counts of Flanders enlarged their estate through a series of diplomatic manoeuvres. The counties of Hainaut, Namur, Béthune, Nevers, Auxerre, Rethel, Burgundy, and Artois were acquired via marriage with the respective heiresses. The County of Flanders itself suffered the same fate. By the marriage of Margaret III, Countess of Flanders with Philip the Bold, Duke of Burgundy, the county and the subsidiary counties were absorbed into the Duchy of Burgundy in 1405.
The geography of the county of Flanders only partially overlaps present day Flanders in Belgium. The land covered by the county of Flanders is spread out over:
Belgium
France
Netherlands
From Wikipedia
Name Format
We follow the ordinary ‘rule’ of using original language. Since we in Belgium have three languages, Flemish/Dutch, Wallon/French and German, but in Flandres was and is the language Flemish/Dutch, we try to incorporate sometimes also the French version, but the Dutch/Flemish version prevales.
The English form should thus be put in the Nickname and Addit field only
The languages used in this area were old forms of Dutch/Flemish and French (not English), thus the names are allowed to be written in those old languages.
Map of the Dutch and Flemish languages