The County of Flanders was one of the most powerful political entities in the medieval Low Countries, located on the North Sea coast of modern-day Belgium and north-eastern France. Unlike the neighbouring states of Brabant and Hainaut, it was within the territory of the Kingdom of France. The counts of Flanders held the northernmost part of the kingdom, and were among the original twelve peers of France. For centuries, the economic activity of the Flemish cities, such as Ghent, Bruges, Ypres and Lille, made Flanders one of the most affluent regions in Europe, and also gave them strong international connections to trading partners.
Up to 1477, the core area under French suzerainty was west of the Scheldt. Historians call this area "Royal Flanders" (Dutch: Kroon-Vlaanderen, French: Flandre royale). Aside from this, the counts, from the 11th century onward, held land east of the river as a fief of the Holy Roman Empire, and this is referred to as "Imperial Flanders" (Rijks-Vlaanderen or Flandre impériale). From 1384, the county was politically united to the Duchy of Burgundy, and it formed the starting point for more acquisitions in the area, and the eventual creation of the Burgundian Netherlands. The expansion of Flemish ("Burgundian") power deep into the Holy Roman Empire further complicated the relationship between Flanders and France, but reinforced the connections with Brabant, Hainaut, Holland and other parts of the Low Countries. The link to the empire was strengthened even more when the Burgundian Netherlands came into the hands of the imperial Habsburg dynasty in 1477. Most of Flanders became part of the empire after the Peace of Madrid in 1526 and the Peace of the Ladies in 1529, although it came to be ruled under the Habsburg crown of Spain. Most of the old county's territory lies outside of present-day France, one of only two parts of medieval France that are no longer part of the country; the other being Catalonia, renounced in 1258.
By 1795, the entire Austrian Netherlands, the successor of the Spanish Netherlands, was acquired by France under the French First Republic, and this was recognized by treaty in 1797. After the 1815 Battle of Waterloo, these territories, including most of the old county of Flanders, passed to the newly established United Kingdom of the Netherlands, which was split up between 1830 and 1839 into the modern countries of Belgium, Luxembourg and the Netherlands. Although the French Republic had avoided using the names of the great medieval counties for their administrative départements, the Dutch and Belgian regimes brought back such names, and as a consequence the two westernmost provinces of the Flanders region of modern Belgium are now called West Flanders and East Flanders.
The term Flanders originally referred to the area around Bruges. It is first mentioned in the biography of Saint Eligius (c. 590–660), the Vita sancti Eligii. The work was written before 684 but has been known only since 725. This work mentions only the place "in Flandris".
A Germanic etymology for Flanders and Flemish (Dutch: Vlaanderen, Vlaams) was proposed by Maurits Gysseling in 1948, based upon an article by René Verdeyen in 1943.
According to this proposal, the terms Flanders and Flemish are likely derived from words derived from Proto-Germanic *flaumaz, meaning stream, current, flood or eddy. Based on this, it is proposed that there was a proto-Germanic term *flaumdra that referred to waterlogged land. According to Toorians, the strength of this proposal is that it would describe the salt marshes and mud flats of this low-lying coastal region. It was regularly inundated, before the development of dykes, which started around 1050. However, a weak point of the proposal is that the Germanic wordforms it requires are not found in any records of Dutch or its dialects. Comparison was instead based upon Old High German flewen and flouwen, and Old Norse flaumr.
The geography of the historic County of Flanders is similar to the modern Belgian provinces of West Flanders and East Flanders, although parts of the historic county are now in France and the Netherlands. In modern Belgium, East and West Flanders are only the western extremity of the five provinces of what is now called Flanders. The land covered by the medieval county is spread out over several modern territories:
two of the five Flemish provinces: West Flanders and East Flanders
part of the Flemish province of Antwerp: the land of Bornem
part of the Walloon province of Hainaut: Tournaisis and the region around Moeskroen (that belonged to West Flanders until 1962)
French Flanders (in the Nord departement)
the French westcorner: the region around Dunkirk, Bergues and Bailleul, an area where Flemish used to be the main language
Walloon Flanders, where the Picard language, closely related to French, was spoken.
Artois (in the Pas-de-Calais department): removed from Flanders in 1191 and created as independent county in 1237
Zeelandic Flanders, a region between Belgium and the Western Scheldt in the southern part of the modern province of Zeeland, which from 1581 formed part of the Generality Lands under control of the Dutch Republic.
The arms of the County of Flanders were allegedly created by Philip of Alsace, count of Flanders from 1168 to 1191; a climbing or rampant black lion on a gold field. In the story about the Battle of the Golden Spurs, the arms and its corresponding battlecry Vlaendr'n den leeuw ("Flanders, the Lion") plays a crucial role in the forming of a Flemish consciousness, which was popularised in the 19th century by the book De Leeuw van Vlaanderen by Hendrik Conscience. As a result, the arms of the county live on as arms of the Flemish community.
It is said that Philip of Alsace brought the lion flag with him from the Holy Land, where, in 1177, he supposedly acquired it in battle with a Saracen knight, but this is a myth. The simple fact that the lion appeared on his personal seal since 1163, when he had not yet taken one step in the Levant, disproves it. In reality Philip was following a West-European trend. In the same period lions also appeared in the arms of Brabant, Luxembourg, Holland, Limburg and other territories. The lion as a heraldic symbol was mostly used in border territories and neighbouring countries of the Holy Roman Empire. It was in all likelihood a way of showing independence from the emperor, who used an eagle in his personal arms. In Europe, the lion had been a well-known figure since Roman times, through works such as the fables of Aesop.
The future county of Flanders had been inhabited since prehistory. During the Iron Age, the Kemmelberg formed an important Celtic settlement. During the time of Julius Caesar, the inhabitants were part of the Belgae, a collective name for all Celtic and Germanic tribes in the north of Gaul. For Flanders, specifically these were the Menapii, Morini, Nervii and Atrebates.