The Irish famine of the 1840s had a dramatic effect both on the population within Ireland and the populations of countries such as the US, the UK and Australia, which received the bulk of the Irish diaspora resulting from the famine (Kenny 2003). As such, the effects of the famine have been examined extensively across a range of disciplines. It is therefore a challenge to provide any new perspective on this well-researched area. However, this paper provides novel insights into the spatial effects of the famine on population in two ways. Firstly, we present the most spatially detailed data recorded to date on population change in the period 184151 covering the famine. We are able to do this by, for the first time, linking census data from 1851 (which also records 1841 population) to the boundaries of 3436 Electoral Divisions (EDs) to provide a very detailed description of the uneven nature of population change during the famine decade. Secondly, by collecting data at the same spatial scale for over 100 other variables, we are able to analyse the relationship between population change during this decade and various demographic, locational and land use characteristics of EDs. We do this through not only traditional regression but also by geographically weighted regression (GWR), which allows us to investigate possible spatial variations in the determinants of population change during the famine period. The results of this analysis raise a series of intriguing new questions relating to the effect of the Irish famine on population change and point the way to further detailed historical and geographical research on this important topic. The research also demonstrates the use of GIS and spatial analytical techniques in historical geography as a means of uncovering new questions that can be answered by further qualitative research.