Data underlying geometric morphometric analysis of red squirrels (Sciurus vulgaris) from Great Britain collected between 1948 and 2020. All specimens housed at National Museums Scotland, Edinburgh. Accession numbers in file names. All data collected by by Kim Chandler between 2021 and 2022. 161 crania were scanned in 3D with an Artec Space Spider structured light scanner (Artec3D, Luxembourg) and saved as STL files. 388 mandibles were photographed in 2D with a Nikon 3200 DSLR camera (Nikon Corporation, Tokyo).Landmarks and semi-landmarks were collected from the crania in 3D using Avizo Lite v9.2 (Thermo Fisher Scientific, Waltham, MA), and from the mandibles in 2D using TPSdig2 (Rohlf, 2015). Geometric morphometric analyses were carried out with the Arothron package in the R statistical environment.