Sámuel Gyarmathi (Hungarian: Gyarmathi Sámuel) (July 15, 1751, Kolozsvár — March 4, 1830, Kolozsvár) was a Hungarian linguist, born in Cluj (then Kolozsvár, Transylvania).
He is best known for his systematic demonstration of the comparative history of the Finno-Ugric languages in the book Affinitas linguae hungaricae cum linguis fennicae originis grammatice demonstrata (1799), which rested on the earlier work of János Sajnovics.