Chain O? Lakes State Park is a water recreation and park facility located in the McHenry and Lake Counties of the state of Illinois. Its main body is found in Spring Grove, Illinois and is owned and operated by the state through its Department of Natural Resources.

Chain O? Lakes State Park is a popular water recreation site in the region. The area around the park itself is known for the largest concentration of natural lakes in the state and the park borders and provides access to several of the largest lakes in the chain. The lakes around the park borders include the Grass, Marie, and Nippersink lakes. The park also offers access to the Fox River which in turn connects to seven other lakes in the Chain. The Fox River chain includes the Bluff, Fox, Pistakee, Channel, Petite, Catherine, and Redhead Lakes.