Which lake does not border the state of Michigan?

The lake that does not border the state of Michigan is Ontario. While Michigan shares borders with Lakes Erie, Superior, and Michigan itself, it does not adjoin Lake Ontario.

To understand this within the context of the Great Lakes, it's useful to recognize that Michigan is uniquely positioned between Lake Michigan and Lake Huron, with connections to Lake Erie and Lake Superior. Lake Ontario, however, is situated to the southeast of Lake Erie and is part of a different system that also includes the Saint Lawrence River. Therefore, while Ontario is geographically close and part of the broader Great Lakes region, it does not directly touch Michigan’s borders.