Back Saint Marys Loch CEB Loch Santes Fair Welsh St. Mary's Loch Danish St Mary’s Loch German St Mary's Loch NN Saint Marys Loch Swedish
| St Mary's Loch | |
|---|---|
 1845 engraving by William Miller after P. Paton | |
  St Mary's Loch | |
| Location | Borders |
| Coordinates | 55°29′40″N 3°11′10″W / 55.49444°N 3.18611°W |
| Type | freshwater loch |
| Basin countries | Scotland |
| Max. length | 5 kilometres (3.1 mi) |
| Max. width | 1 kilometre (0.62 mi) |
St Mary's Loch is the largest natural loch in the Scottish Borders, and is situated on the south side of the A708 road between Selkirk and Moffat, about 72 kilometres (45 mi) south of Edinburgh.