Jean Saint-Lager was a French physician, botanist and botanical historian based in Lyon.

After qualifying in medicine at the Lyon School of Medicine (1847) and as a doctor of medicine at the University of Paris (1850), Saint-Lager practised in Lyon for 12 years. Then, from 1862, he devoted himself to scientific study, travelling to make collections for his research on both botanical and medical topics.

Among Saint-Lager's projects was a catalogue of the vascular plants of the Rhone Basin, which he published over the course of 10 years (Catalogue des plantes vasculaires du bassin du Rhone, 1873-1883). He was also particularly interested in botanical nomenclature and the history of botanical collecting. His publications on this topic include Réforme de la nomenclature botanique (1880), Histoire des herbiers (1885) and Recherches sur les anciens herbaria (1886).

Saint-Lager was one of the founding members of the Société botanique de Lyon and served as librarian for that society and for the the Société linnéenne de Lyon, until 1911.

Sources:
C. Roux and O. Meyran, 1913, La vie et les travaux du docteur J.-B. Saint Lager
F.A. Stafleu and R. Cowan, 1985, Taxonomic Literature II, 5: 1073.