George Thomson (c. 1619–1676) was an English physician, medical writer and pamphleteer. He was a leading figure in an attempt to create a "College of Chemical Physicians", a rival to the established Royal College of Physicians. He rejected the traditional Galenic approach to medicine and argued against medical bloodletting, purging and the doctrine of curing by "contraries". He performed a splenectomy on a dog which stimulated debate in scientific and medical circles, and challenged prevailing medical theories about the body.