Old Fort is a census-designated place located in northern Pleasant Township, Seneca County, Ohio, United States;[2] located about a mile east of Ohio State Route 53 where N. Township Rd.

73 intersects with E. County Rd.

Old Fort was platted in 1882, and named after Fort Seneca, a fort built during the War of 1812.

[4] A post office has been in operation at Old Fort since 1882.

[5] Old Fort sits adjacent to the Sandusky River, which is a tributary to Lake Erie.