S
- St. Laurence's Stream, County Dublin
- St. Margaret's Stream, County Dublin
- Santa Sabina Stream, County Dublin
- Santry River, County Dublin
- Scribblestown Stream, County Dublin
- Shallon Stream, County Dublin
- Shanganagh River, County Dublin
- Shannon — longest river on the island. Develops into Lough Allen, Lough Bofin, Lough Ree and Lough Derg along its course.
- Shimna*
- Sillees*
- Silver
- Six Mile Water*
- Slade Brook, County Dublin
- Slaney, County Wicklow, County Carlow and County Wexford
- Slang River, County Dublin
- Sluice River, County Dublin
- Smearlagh River, County Kerry
- Sruh Croppa*
- Stein River, County Dublin
- Stoneyford
- Strule*
- Suck
- Suir
- Swan River, County Dublin
- Swanlinbar (also known as Cladagh)*
- Swilly
Read more about this topic: Rivers Of Northern Ireland