Nemacolin's Trail, or less often Nemacolin's Path, was an ancient Native American trail that crossed the great barrier of the Allegheny Mountains via the Cumberland Narrows Mountain pass, connecting the watersheds of the Potomac River and the Monongahela River in the present-day United States of America. Nemacolin's Trail connected what are now Cumberland, Maryland and Brownsville, Pennsylvania.

The path was a network of trails that had long been used by indigenous peoples in pre-colonial America. Nemacolin's Path starts near present-day Cumberland, Maryland, continuing on to Brownsville, Pennsylvania to the neighborhood known today as Redstone located at mouth of Redstone Creek. In colonial America, the site was known as Redstone Old Fort for its defensive installation.

During 1749 and 1750, the Delaware Indian chief Nemacolin and Maryland frontiersman Thomas Cresap supervised improving the trail for the Ohio Company, at the behest of Christopher Gist. They developed the template trail and in large part the route for what became known on the eastern slopes as the eastern part of Braddock's Road. In 1755, the eastern part of Nemacolin's Path was used as military route by British General Edward Braddock in his attempt to capture Fort Duquesne.