Canyon County is located in the U.S. state of Idaho. As of the 2020 Census, the population was 231,105, which by 2022 was estimated to have risen to 251,065. making it the second-most populous county in Idaho. The county seat is Caldwell, and its largest city is Nampa. Canyon County is part of the Boise metropolitan area.

Caldwell is a city in and the county seat of Canyon County, Idaho. The population was 59,996 at the time of the 2020 United States census, making it the 5th most populous city in Idaho.