The Blue Hole is a fresh water pond and cenote located in Castalia, Erie County, Ohio, in the United States.

From the 1920s to 1990 the Blue Hole was a tourist site, attracting 165,000 visitors annually at the height of its popularity, partly because of its location on State Route 269, about 7 miles (11 km) southwest of the Cedar Point amusement park in Sandusky, Ohio.

Contrary to prevalent belief, the depth of the Blue Hole is not unknown, but has been sounded and found to be about forty-three to forty-five feet (13.1 to 13.7 m) deep.

The Blue Hole is fed by a passing underground stream which discharges 7 million US gallons (26,000 m3; 5.8×10^6 imp gal) of water daily into Sandusky Bay to the north, feeding into Lake Erie.

It is to be distinguished from another cenote, similar in size and eerie bluish-green color, owned by the Castalia State Fish Hatchery and operated by the Ohio Department of Natural Resources, Division of Wildlife, which is open for public viewing and which has grown in popularity since the closure of the Blue Hole in the late 1990s.