Abstract. The connections between science and civic culture in the Victorian period have been extensively, and intensively, investigated over the past several decades. Limited attention, however, has been paid to Irish urban contexts. Roman Catholic attitudes towards science in the nineteenth century have also been neglected beyond a rather restricted set of thinkers and topics. This paper is offered as a contribution to addressing these lacunae, and examines in detail the complexities involved in Catholic engagement with science in Victorian Belfast. The political and civic geographies of Catholic involvement in scientific discussions in a divided town are uncovered through an examination of five episodes in the unfolding history of Belfast's intellectual culture. The paper stresses the importance of attending to the particularities of local politics and scientific debate for understanding the complex realities of Catholic appropriations of science in a period and urban context profoundly shaped by competing political and religious factions. It also reflects more generally on how the Belfast story supplements and challenges scholarship on the historical relations between Catholicism and science.There is now a well-established body of scholarship addressing the interaction of science and urban culture in nineteenth-century Britain. Pioneering work in this field, by scholars such as Arnold Thackray and Ian Inkster, explored the thesis that science was a useful resource for 'marginal men' intent on securing social status in contexts where opportunities to engage in formal politics were significantly curtailed. This work underlined the productive links between science and Protestant dissent, particularly of a heterodox kind. 1 Subsequent studies have demonstrated the ways in which other groups, both within and outside established civic elites, developed and deployed science to serve a range of social and political interests. For example, Michael Neve examined the utilization of science by Bristol's commercial elite to consolidate their Peelite conservatism and Adrian Desmond uncovered the use that Owenite and atheist artisans made of Lamarckian evolution in early nineteenth-century London to buttress radical anti-establishment politics. In the wake of these and other studies, James Secord's