Thomas Ignatius Maria Forster (9 November 1789 – 2 February 1860) was an English astronomer, physician, naturalist and philosopher.
An early animal rights activist, he promoted vegetarianism and founded the Animals' Friend Society with Lewis Gompertz.
He published pamphlets on a wide variety of subjects, among other things, morality, Pythagorean philosophy, bird migration, Sati, and "phrenology", a term that he coined in 1815.