This thesis seeks to examine the history of the naval forces of the Irish state since its independence and identify those factors, events and decisions which shaped their development while also providing an overview of the naval history of the state. Since the foundation of the Irish Free State and the civil war which marked its birth, the Irish state has established several naval forces, generally in times of grave national emergency but little of their history is known to the wider public. Although most are aware of the Irish Naval Service, which came into being after the Second World War, few know of its predecessors. The Coastwatching and Marine Service, later to become the Marine Service, provided seaward defence during the Emergency, the uniquely Irish euphemism for the Second World War. Its many constituent parts were responsible for the patrolling of Irish territorial waters, minesweeping operations and the surveillance of shipping around the Irish coast and those merchant ships which entered Irish ports. Its establishment in 1939 marked the end of a period during which the state maintained no naval forces. The Coastal and Marine Service, distinct from the aforementioned Coastwatching and Marine Service, represented the naval forces of the Irish Free State, towards the end and immediately after the Civil War; it was closely involved with the guerrilla phase of the conflict and the anti-smuggling patrols which followed. During the early months of the Civil war, a naval force was established to aid in the fighting, although it was a nameless and rather unofficial organisation, it conducted amphibious landings and provided vital assistance to the National Army in their campaign to recapture those areas beyond the control of the Provisional Government. The structure of the thesis follows that of the rise and fall of the various services. Each chapter refers to a distinct period which differs from that which came prior and followed. The Civil War, inter-war years and the Emergency are clearly differentiated by the presence of the Coastal and Marine Service, no formal naval force and the Marine Service, respectively and thus provide the first three chapters of this work. The division of the history of the Naval Service into four chapters requires a brief explanation. The service's foundation represented a time of great progress and rapid expansion and is covered by the fourth chapter. The fifth chapter details the stable maintenance of the service during the 1950s. The 1960s see a dramatic reversal in the fortunes of the service and this time of regression is detailed in the sixth chapter. The seventh and final chapter encompasses the 1970s when the service began to once again expand and prosper.