Stanley Marsh, voiced by Trey Parker, is a fictional character in United States television series South Park. He and Kyle trade places as the leader of the four characters.

He is the most normal of the kids, and is generally honest and well-meaning. He is somewhat more assertive than his friend Kyle.

Stan is also notably the "skeptic" of the group, and is often very critical of popular trends. This is evident in episode 407 "Cherokee Hair Tampons" when he challenged the character Miss Information and her shop of alternative medicine, in episode 504 "Super Best Friends" when he helped battle David Blaine's suicidal cult, and in episode episode 615 where he accuses psychic medium John Edward of being the episode's title, "The Biggest Douche in the Universe." However, sometimes Kyle takes on this role, and it is Stan who is the gullible one, such as with the metrosexual trend in "South Park is Gay!"

Stan had a girlfriend named Wendy Testaburger who has since broken up with him; he used to vomit everytime she tried to talk to him.

He is the son of Randy and Sharon Marsh, he has a sister, Shelly (who beats him up on a regular basis), and a gay dog named Sparky. He once owned a killer goldfish (from a parallel universe). His father is a geologist, Nobel Prize winner, and former Boy band member.

He and Kyle switched places on announcing Kenny's death by saying "Oh my God, they killed Kenny!" Usually followed by the other saying "You Bastards." This became less and less emphatic over the years as Kenny continued to die.

He wears a dark blue hat with red trim and poofball, a brown coat, blue pants, and red mittens. Stan rarely takes off his hat, but underneath is shaggy black hair.