The paper presents the development and implementation of a geo-spatial model for mapping populations’ access to specified types of water and sanitation services in Nigeria. The analysis uses geo-referenced, population-representative data from the National Water and Sanitation Survey 2015, along with relevant geo-spatial covariates. The model generates predictions for levels of access to seven indicators of water and sanitation services across Nigeria at a resolution of 1 × 1 km2. Overall, the findings suggest a sharp urban–rural divide in terms of access to improved water, basic water, and improved water on premises, a low availability of piped water on premises and of sewerage systems throughout the country, a high concentration of improved sanitation in select states, and low rates of nationwide open defecation, with a few pockets of high rates of open defecation in the central and southern non-coastal regions. Predictions promise to hone the targeting of policies meant to improve access to basic services in various regions of the country.