Salinization is a growing concern of global proportions. In urban settings effective salinity management strategies must be adopted to ensure environmental sustainability in the face of rapid development. Geophysical methods, particularly electrical methods, can be used to non-invasively map the spatial distribution of subsurface groundwater salinity over wide areas at reasonable cost. In this paper, electrical resistivity tomography and vertical electrical sounding geophysical methods were used to determine the electrical resistivity structure of the subsurface beneath the rapidly developing Khon Kaen University campus in NE Thailand. The geophysical results were combined to generate a contour map of depth to saline groundwater beneath the campus. Saline groundwater was present in shallow strata in the southern part of the campus but is not indicated beneath the northern half, so that drilling for groundwater wells is recommended there. The map can be used by campus planners to inform their salinity management strategies, including the siting of groundwater wells, the design of potential soil reclamation schemes, and the location and design of buried infrastructure according to indications of soil corrosivity. The method can be applied at other urban sites located on salt-affected lands and, in general, provides a valuable supplement to costly traditional geotechnical testing.