According to music scholar Nicholas Carolan, the combined tune collections and scholarly publications of Francis O’Neill (1848-1936) constitute “the largest snapshot of [Irish] music ever taken in its 9,000-year history” (1997: 60). Yet O’Neill has largely been celebrated in that history as an Irish folk musician and ‘saviour’ of endangered traditional Irish melodies rather than as an idiosyncratic, amateur scholar whose writings may be put into productive dialogue with various trends in European musical folklore and intellectual thought in the long nineteenth century. Francis O’Neill extensive personal library suggests an approach to collecting and studying Irish music beyond an insular, ethno-nationalist perspective. His publications (1903-1922) draw upon repertoires and intellectual discourses from historical sources and from eighteenth- and nineteenth-century, antiquarian-inspired outputs from across Ireland, Scotland, the United Kingdom and Europe. O’Neill simultaneously developed specific approaches to fieldwork as a participant-observer, ethnographic vignette writer, and tune collector in contemporary performance contexts, marking him as a prototypical ethnomusicologist. While O’Neill spent most of his life in Chicago, he kept in regular contact with music and language scholars in Ireland engaged in discussions with European counterparts. Ultimately, O’Neill’s works reveal a nationalist-inspired, cosmopolitan approach to music, along with a modernist perspective from an American city full of ethnic Europeans, where access to recording technology and specialist orthographic printing capabilities allowed for the generation of an extensive body of work, singling O’Neill as one of the first to comprehensively document an Irish/European diasporic music community. Drawing up O’Neill’s publications, and on critical perspectives on O’Neill (Bohlman & Stokes 2003; Nolan 2007; Smith 2012), this paper frames O’Neill as both a folk music scholar leaning into continental trends, thereby re-emplacing O’Neill as European, and as an Irish scholar whose work extends our understanding of what constitutes European folk music research in the long nineteenth century.