The County of Hainaut is a historical lordship within the medieval Holy Roman Empire, with its capital at Mons (Dutch: Bergen).

In English sources it is often given the archaic spelling Hainault.

The name comes from the river Haine (Dutch: Hene, German: Henne), which also leads to the German name Grafschaft Hennegau for the County of Hainault.Its most important cities are Mons (Bergen), Cambrai (Dutch: Kamerijk) and Charleroi.

It consists of what is now the Belgian province of Hainaut and the southern part of the French département Nord.