Castlederg (earlier Caslanadergy) is a village in County Tyrone, Northern Ireland. It lies on the River Derg and is near the border with County Donegal. It stands in the townlands of Castlesessagh and Churchtown, in the historic barony of Omagh West and the civil parish of Urney. The village has a ruined castle and two ancient tombs known as the Druid's Altar and Todd's Den. It had an estimated population of 2,935 people in 2008.
The village hosts some of the district's key events each year, including the Derg Vintage Rally and the traditional Apple Fair which sees the apple growers of County Armagh visit to sell their wares.
Traditionally, Castlederg was a traveller's stop along the ancient pilgrimage route to Station Island on Lough Derg. The town boasts ancient ruins, monastic settlements and, as the stories go, has connections to Davy Crockett and Joe Sheridan, the creator of Irish coffee.