Waterloo County was a county in Canada West in the United Province of Canada from 1853 until 1867, then in the Canadian province of Ontario from 1867 until 1973. It was the direct predecessor of the Regional Municipality of Waterloo.

Situated on a subset of land within the Haldimand Tract, Waterloo County consisted of five townships: Woolwich, Wellesley, Wilmot, Waterloo, and North Dumfries. The major population centres were Waterloo, Kitchener (known as Berlin prior to 1916), Preston, Hespeler, Blair, and Doon in Waterloo township; Galt in North Dumfries; Elmira in Woolwich; and New Hamburg in Wilmot. All are now part of the Regional Municipality.

Waterloo County was once one of the most densely wooded sections in North America. Oak trees three to four feet in diameter, maple, beech, elm, ash oak and great pines were common. The county, located in the northerly edge of Attawandaron land, was excellent for hunting and fishing.

In 1784, by way of the Haldimand Proclamation, the British Government granted the Grand River valley to Six Nations (AKA Iroquois Confederacy) refugees from central and western New York State, indigenous peoples who served as allies during the American Revolution. The area was from Lake Erie to the Elora falls, and the width being six miles on each side of the river. The First Nations soon offered almost half of the upper area for sale. It was divided into four blocks. Blocks 1, 2 and 3 were sold by 1816; this large area became the townships of Waterloo, Woolwich and Dumfries.

The western part of this area was initially settled by Mennonites of German extraction from Pennsylvania; most settled the area that would become Kitchener, St. Jacobs, Elmira and surroundings. The southern part (now Cambridge) – as well as areas that would become Fergus and Elora, just outside Waterloo County – were settled by Scots. Except for grist, woolen and saw mills, there was little industry in any of these area until about 1870.

Settlement of the what later became the Township of Waterloo started in 1800 (in an area that is now a part of Kitchener) by Joseph Schoerg (later called Sherk) and Samuel Betzner, Jr. (brothers-in-law), Mennonites, from Franklin County, Pennsylvania. At the time, the upper part of the Grand River Valley was considered deep in the wilderness, and was difficult to penetrate into with wagons due a lack of roads. One Waterloo County historian, W. H. Breithaupt, believed that Schoerg and Betzner, after arriving in Upper Canada, travelled from Ancaster westward through Beverley Township to a point on the Grand River near where Paris would later be founded, using a road cut through the wilderness the previous year by two Englishmen named Ward and Smith. They then followed the Grand River northward. Joseph Schoerg and his wife settled on Lot 11, B.F. Beasley Block, S.R., on the bank of the Grand River opposite Doon, and Betzner and his wife settled on the west bank of the Grand, on a farm near what would become the village of Blair.

The homes built by the next generation of these families still stand as of March 2021, on what is now Pioneer Tower Road in Kitchener, and have been listed as historically important; the John Betzner homestead (restored) and the David Schoerg farmstead (not yet restored) were erected circa 1830.

The German Company, represented by Daniel Erb and Samuel Bricker, had gotten into financial difficulties after buying the land in 1796 from Joseph Brant who represented the Six Nations. The payment to Beasly, in cash, arrived from Pennsylvania in kegs, carried in a wagon surrounded by armed guards.