| Forstegg Castle | |
| Native Name: | Burg Forstegg |
| Built: | about 1200 |
| Type: | hill castle |
| Condition: | ruin |
| Location: | Sennwald |
| Occupants: | Freiherr of Sax/Misox |
| Coordinates: | 47.2456°N 9.4958°W |
| Map Type: | Switzerland |
| Code: | CH-SG |
Forstegg Castle is a ruined castle in the municipality of Sennwald of the Canton of St Gallen in Switzerland. It was built around 1200 by the Barons of Sax/Misox, was abandoned in the 19th century and fell into ruin in 1894.