Gaster may refer to:
People and fictional characters Gaster (surname) Gaster Nsereko (born 1965), Ugandan Anglican bishop W.D. Gaster, a character from the video game Undertale Sir Gaster, a character in the book Le Quart Livre by François Rabelais Gaster, a character in the television series PaRappa the Rapper
Other uses Gaster (insect anatomy), an insect body part a trade name of famotidine, an inhibitor of stomach acid production Gaster District, a former district in St. Gallen, Switzerland that later became the See-Gaster constituency