Water isotope analyses can be used as tracers in water resource sustainability, forensics (e.g. human, ecological, food authenticity and provenance) and climate research, however, limited research has been conducted on water in Mexico. This first national-level tap water survey of coupled H-O isotope ratios is reported from over 50 cities and towns across Mexico. Tap water across the country records a range of 82.4‰ for δ2H and 12.0‰ for δ18O, analyzed using a Picarro L2130-i analyzer. The isotopic values show strong relationships (r > 0.5) with the geography as well as some social and socioeconomic parameters. A Geographic Information System approach is used to develop maps of predicted tap water isotope ratios (isoscapes) for Mexico. These isoscapes will be useful to researchers interested in human-hydrological systems as well as forensic scientists establishing the region of origin or the travel history recorded by human remains.