Mount Tammany is the southernmost peak of the Kittatinny Mountains in Knowlton Township, Warren County, New Jersey, United States. It is tall, and forms the east side of the Delaware Water Gap. Across the Gap is Mount Minsi, on the Pennsylvania side of the river. The mountain is named after the Lenni Lenape chief Tamanend. It lies along the Appalachian Trail in Worthington State Forest. The summit can be hiked by the Mount Tammany Trail ascending the western slopes. This trail head is accessible from Interstate 80.