Fort Seybert was an 18th-century frontier fort in the Allegheny Mountains in what is now Pendleton County, West Virginia, United States. In a 1758 surprise raid occasioned by the French and Indian War (1754–63), most of the 30 white settlers sheltering there were massacred by Shawnee and Delaware warriors and the fort was burned. A similar number of settlers at nearby Fort Upper Tract had met the same fate on the previous day. Fort Seybert, of which almost no trace remains today, was situated about 8 miles northeast of the present town of Franklin.
After the defeat of General Edward Braddock at the Battle of the Monongahela (9 July 1755), the white settlers of the Allegheny Mountains were largely unprotected from a series of Shawnee and Delaware Indian raids. By the end of the year, the Virginia Regiment had increased its numbers by several hundred troops and began to temporarily man some of the settler forts that had been hastily thrown up by civilians or soldiers. Fort Seybert was built on the South Fork of the South Branch of the Potomac River within about 100 yards of a pre-existing structure known as John Patton's Mill. Patton had owned the land since 1747, but sold it in 1755 to Jacob Seybert.
Colonel George Washington, the new 24-year-old commander of the Virginia Regiment, embarked on a campaign to protect the settlers of the upper South Branch and surrounding region by building up and manning frontier forts. Among the official records of forts, local militias and Indian raids, Washington and his officers occasionally mention both Fort Upper Tract and Fort Seybert, either by location or name, along with other forts on the South Branch and the South Fork. In August 1756 Washington wrote to Virginia Lieutenant Governor Robert Dinwiddie to say that