Harvey Cox describes Pentecostalism as “the fascinating spiritual child of our time” that has the potential, at the global scale, to contribute to the “reshaping of religion in the twenty-first century.” This study grounds such sentiments by examining at the local scale the origin, development and nature of Pentecostalism in Ireland in its first twenty years. Illustrative, in a paradigmatic way, of how Pentecostalism became established within one region of the British Isles, it sets the story within the wider context of formative influences emanating from America, Europe and in particular, other parts of the British Isles. As a synoptic regional study in Pentecostal history it is the first survey of its kind.