Lough Derg stretches between Killaloe in County Claire and Portumna in County Galway. It is the largest lake on the River Shannon. It is a natural mixed fishery offering superb angling, primarily for pike and course fish. Geologically-speaking Lough Derg is a lake of two parts, each with very distinct characteristics. The northern half features headlands, islands and shoals of boulder-rich glacial drift surrounded by the natural beauty of rural countryside. The southern end is much more dramatic as its deep, almost 30 metres, waters are channelled through the sheer gap it cuts between Slieve Bernagh and Arra mountains.

The lake is a natural mixed fishery offering superb angling, primarily for pike and coarse fish, but with a good stock of wild brown trout which are most popularly fished during the Mayfly season. A remarkable inhabitant of Lough Derg is the Croneen trout – a migratory brown trout that breeds in its tributaries in north Tipperary and south Offaly. This unusual brown trout has characteristics similar to sea trout in behaviour. Shoals of big bream, tench, roach and perch roam its depths and these can be successfully fished from an anchored boat alongside weedbeds. There is a lot of natural access for shore fishing, however, a stretch of shoreline has been developed with fishing stands at Twomilegate near Killaloe. This stretch has become famous for its remarkably consistent big catches of good bream.

The European Pike Angling Challenge is an annual event on Lough Derg and normally takes place during the third week in September. The immense geography of Lough Derg is not comprehensible as one fishery, it is best addressed from one of the many well-established angling centres which surround the lake. Angling on the lake is mainly by boat, and hire facilities are available from well-equipped fishing centres in towns and villages around its perimeter, at Killaloe, Scarriff, Mountshannon, Whitegate, Portumna, Terryglass, Kilgarvan, Dromineer, Garrykennedy and Ballina.