Y Llethr
| Country | Wales |
|---|---|
| Area | Snowdonia |
| Translation | The slope (Welsh) |
| Elevation | 756 m (2,480 ft) |
| Relative height | 561 m |
| OS grid reference | SH661258 |
| OS Landranger map(s) | 124 |
| Listing | Marilyn, Hewitt |
Y Llethr is the highest mountain in the Rhinogydd of Snowdonia, north Wales. The shortest route to the summit goes from Cwm Nantcol in the west, either directly or via Bwlch Drws Ardudwy and over Rhinog Fach.