Flanders (Vlaanderen in Dutch, Flandre in French) is a region in Belgium, consisting of the provinces of Antwerp, West Flanders, East Flanders, Flemish Brabant and Limburg, all located in the northern part of Belgium, with Antwerp in the northwest, and Limburg in the northeast.
The population, about 6 million people, speak a dialect of Dutch, called Flemish. The city of Antwerp (which is the capital of the province Antwerp) is, because of its large harbor, the most important city.

In Roman times, the area was inhabited by Romanized Celts. Then more and more Gothic Germans came to live there, and in the 3rd and 4th century A.D., the Salic Franks came from the north and drove back the Romans to approximately the area that now divides Flanders from the French speaking part of Belgium, where the Walloons live.
In the 5th century, the Roman garrisons left, and the Franks pushed on further south. The ones that went south adopted the language that was spoken there, which has become what we now know as French, but the Franks that stayed in the north retained their Germanic language, what over the years has become what we now know as Dutch. This is why in Flanders they speak Dutch, and in the south they speak French.