Walloons
The Walloons are French-speaking Belgians from Wallonia. (Wallons in French.) They are one of the two major groups in Belgium, the other being the Dutch-speaking Flemish. The french-speaking inhabitants of Brussels do not generally see themselves as Walloons.
In most of the 20th century and up to now, the Flemish have been politically and economically dominant over the Walloons. This hasn't always been so. During the first century of its existence and more, French practically was the unique official language of Belgium. Before the crisis of mining industries the Walloons in southern Belgium were dominant. There are the reason why French rather than Dutch was the colonial language in Congo.
Note that when referring to inhabitants of Wallonia with the meaning of citizen of Wallonia, the word Wallonian is more commonly used. Not all Wallonians are French-speaking, there is also a German-speaking community around Eupen, in the east of the region, next to Germany.
Walloon (Walon) is also a romance language spoken in Wallonia, in a small portion in north of France and in the Green Bay region of Wisconsin, USA (where an important number of Walloon settlers came in the 19th century).