Derrycassan (from Irish: Doire an Cásain meaning either the "Path through the Oakwood" or "Cassan's Oakwood" (Cassan being an early Irish form of the present name Cassidy) is a townland in the civil parish of Templeport, County Cavan, Ireland. It lies in the Roman Catholic parish of Templeport and barony of Tullyhaw. The local pronunciation is Dorrahasson.