- River Maigh
- Co. Limerick.
- Ros da Shioleach
- Limerick.
- Ruirlech
- Liffey.
- Samair
- R. Cumhair, runs through Bruff.
- Sionnan
- River Shannon.
- Siuir Beoir and Berba
- River Suir, Co. Tipperary. Siuir and Suir and Nore and Barrow.
- Slieve Baisne
- Co. Roscommon.
- Slieve Bladmai
- Slieve Bloom.
- Slieve Buane
- Slieve Banne, Co. Roscommon.
- Slieve Conaill
- Border of Leitrim and Donegal.