Big Otter is an unincorporated community in Clay County, West Virginia, United States. Big Otter is located on Big Otter Creek at the junction of Interstate 79 and West Virginia Route 16. The community is 9.5 miles north-northeast of Clay, the county seat of Clay County. Big Otter is part of ZIP code 25113. Its original post office with a zip code of 25020 closed in 1979.