Fründsberg is an abandoned hilltop castle in the Tössbergland, above the hamlet of Oberholz in the municipality of Eschenbach (canton of St. Gallen), on the canton border between St. Gallen and Zurich.
The castle stood on a ledge from Nagelfluh, on a western branch of the Höchhand (Chrinnenberg). It was separated from the mountain by a throat ditch eight meters deep. One pillar that may have supported an access bridge has been preserved.