Silly (; ; ) is a municipality of Wallonia located in the province of Hainaut, Belgium.
On January 1, 2018, Silly had a total population of 8,407. The total area is which gives a population density of 118 inhabitants per km<sup>2</sup>.
The name of the town derives from its stream, called the Sille (French) or Zulle (Dutch), and has no relation to the English word. In the English-speaking world, it has frequently been noted on lists of unusual place names.
The municipality consists of the following districts: Fouleng, Gondregnies, Graty, Hellebecq, Hoves, Silly, Thoricourt, and Bassilly.
Silly is twinned with: