Data underlying geometric morphometric analysis of red squirrel (Sciurus vulgaris) mandibles from Great Britain collected between 1948 and 2006. All specimens housed at National Museums Scotland, Edinburgh. Accession numbers in file names. All data collected by by Philip Cox. All mandibles were photographed in 2D with a Nikon 3200 DSLR camera (Nikon Corporation, Tokyo). This data is analysed in Cox et al (2020) J. Zool. 312: 271-283 doi: 10.1111/jzo.12829