| Iltiosbahn | |
| Other Name: | Standseilbahn Unterwasser–Iltios; Drahtseilbahn Unterwasser-Iltios |
| Status: | In operation |
| Start: | "Unterwasser (Iltiosbahn)" at Frühweidstrasse 8 |
| End: | "Iltios" |
| Stations: | 2 |
| Routenumber: | 2767 |
| Event1label: | Concession |
| Event1: | 1933 |
| Event2label: | Enhancements |
| Event2: | 2005 |
| Owner: | Toggenburg Bergbahnen AG (since 2008) |
| Operator: | Toggenburg Bergbahnen AG (short: TBB) |
| Stock: | 2 |
| Maxincline: | 27% |
| Electrification: | from opening |
| Elevation M: | 1339 |
| Map State: | uncollapsed |
Iltiosbahn is a funicular railway in the Canton of St. Gallen, Switzerland. It leads from Unterwasser at 911 m to Iltios at 1339 m, from where an aerial cableway continues to Chäserrugg (2262 m), a peak of the Churfirsten range above Lake Walen. The line has a length of 1195 m with a maximum incline of 27% and a difference of elevation of 428 m.
The funicular is owned and operated by Toggenburg Bergbahnen AG.
The railway was built in 1934, the aerial lift 1972.