Iroquois County is a county located in the northeast part of the U.S. state of Illinois. According to the 2020 United States Census, it has a population of 27,077. It is the only county in the United States named Iroquois. The county seat is Watseka. The county is located along the border with Indiana.

Watseka is a city in and the county seat of Iroquois County, Illinois, United States. It is located approximately 15 miles (24 km) west of the Illinois-Indiana state line on U.S. Route 24.