Samuel Powel Griffitts (July 21, 1759 – May 12, 1826, sometimes also written as "Griffiths") was an American physician, widely regarded as the founder, in 1786, of the Philadelphia Dispensary (a free clinic for poor people).

Together with his classmate Caspar Wistar, Griffitts was one of the medical volunteers who treated wounded soldiers after the nearby Battle of Germantown.

[7] Benjamin Rush gave him a list of eighteen recommendations for medical students in Europe:[7]Rush recommended that .. Griffitts attend lectures on natural philosophy as well as on medical subjects, visit the hospitals, noting the prescriptions and modes of treatment, spend a few hours daily for some weeks in a chemical laboratory and apothecary's shop, and acquire a library...and spend an hour daily for three months on dancing lessons.Griffitts went first to Paris and then to Montpellier, but transferred his studies to London as soon as hostilities ended, writing to Rush in 1783 that although London was "the Metropolis of the whole world for Practical Medicine" the French hospitals were cleaner and had better nursing arrangements.

Griffitts headed the list of the dispensary's first doctors and continued to make daily visits to its patients for more than forty years.

[10] In 1792, he was elected Professor of Materia Medica at the University of Pennsylvania,[11][12] and held this position for four years before resigning it to Benjamin Smith Barton.