Valentia or Valencia (vəlĕn´shēə), island (1991 pop. 680), c.7 mi (11.3 km) long and 2 mi (3.2 km) wide, off the coast of Co. Kerry, SW Republic of Ireland. Its slate, once famous, is no longer quarried, and the island is now best known as the eastern terminus of the first permanent transatlantic cable, laid (1866) by the Great Eastern and connecting Valentia with Trinity Bay, Newfoundland. The cable station is at Knightstown. Glanleam, the old estate of the knight of Kerry, has subtropical gardens.