Addington County is a historic county in the Canadian province of Ontario.
The county was created in 1792. It was named after Henry Addington, 1st Viscount Sidmouth. In 1800, it was merged with Lennox County to form the united county of Lennox and Addington. Addington was the northern portion of the merged county, which is now the municipalities of Addington Highlands, Stone Mills, and Loyalist.
However, Lennox and Addington elected separate representatives to the Parliament of Canada for many years.
Many of the county's original settlers were Palatine Germans.
See also List of Ontario census divisions.
