Dundas County is a former county in the province of Ontario, Canada. It was named after Henry Dundas, 1st Viscount Melville, who was the British Home Secretary (1791–1794), with responsibility for the colonies.
Dundas was first settled by individuals of European background in 1784, when German Loyalists who had fought with Sir John Johnson in the American Revolutionary War re-settled in Canada. The settlers were descendants of the Palatine immigrants to America in 1710.