Lough Derg, historically Lough Dergart (Irish: Loch Deirgeirt), is a freshwater lake in the Shannon River Basin, Ireland.
It is the third-biggest on the island of Ireland (after Lough Neagh and Lough Corrib).

It is a long, narrow lake, with shores in counties Clare (south-west), Galway (north-west), and Tipperary (to the east).
It is the southernmost of three large lakes on the River Shannon; the others being Lough Ree and Lough Allen.
Towns and villages on Lough Derg include Portumna, Killaloe & Ballina, Dromineer, Terryglass, Mountshannon and Garrykennedy.

The lake's name evolved from the Irish Loch Deirgdheirc.
This was one of the names of The Dagda, an Irish god, and literally means "red eye".
Lough Derg, historically Lough Dergart (Irish: Loch Deirgeirt), is a freshwater lake in the Shannon River Basin, Ireland. It is the third-biggest on the island of Ireland (after Lough Neagh and Lough Corrib).
It is a long, narrow lake, with shores in counties Clare (south-west), Galway (north-west), and Tipperary (to the east). It is the southernmost of three large lakes on the River Shannon; the others being Lough Ree and Lough Allen. Towns and villages on Lough Derg include Portumna, Killaloe & Ballina, Dromineer, Terryglass, Mountshannon and Garrykennedy.
The lake's name evolved from the Irish Loch Deirgdheirc. This was one of the names of The Dagda, an Irish god, and literally means "red eye".
Lough Derg (Shannon)