[ModIr. An tSionna, the old one].
Principal river of Ireland flowing 224 miles south-west from a spring under Cuilcach Mountain, Co. Cavan, to the Atlantic. In its last seventy miles the river becomes a wide estuary; between counties Roscommon, Longford, and Westmeath, it widens to form Lough Ree, and above Killaloe, between Clare, Galway, and Tipperary, it forms Lough Derg (2). For much of its length the Shannon forms the border between Connacht on the west and Leinster and Munster on the east and south, and thus in much of Irish literature the river's name implies a border. Surprisingly, considering its size and importance in Irish transportation and commerce, and its frequent citation in early Irish literature, the Shannon is less mythologized than the Boyne. The goddess of the Shannon, Sinann, is linked to the Boand, goddess of Boyne, through the Well of Segais. In stories from oral tradition, the Shannon was formed by the dragon-like oilliphéist [Ir., great beast] fleeing St Patrick. Midach's enchanted Hostel of the Quicken Trees in the Fenian story Bruidhean Chaorthainn is located on the Shannon. Much action along the river focuses on its principal ford Athlone [the ford of Luan]. Along the Shannon's lower reaches, under the estuary, is thought to lie Shannon City, which appears above water every seven years; mortals who see it will die. See SUBMERGED CITIES. Known in Manx as Yn hannon; W Llinon. See Padraic O'Farrell, Shannon Through Her Literature (Dublin, 1983).