The two largest ethnic groups of Belgium are Flemish and Walloon.

The statement is true because Flemish and Walloon are indeed the two largest ethnic groups in Belgium. Flemish refers to the Dutch-speaking population of Belgium, primarily residing in the northern region of Flanders. On the other hand, Walloon refers to the French-speaking population mainly concentrated in the southern region of Wallonia. These two groups together comprise the majority of the Belgian population, with Flemish being the largest ethnic group and Walloon being the second largest. The division between Flemish and Walloon is a significant aspect within Belgian society, impacting politics, language, and cultural identity in the country.