Stanley "Stan" Marsh is one of South Park's main characters along with Kyle Broflovski, Eric Cartman, and Kenny McCormick, and serves as the main protagonist of the franchise.

He is described as friendly, knowledgeable, helpful, and relaxed, and is also the most tender and sensitive of the main characters. He is also the oldest of the four main boys, having his tenth birthday in "You're Getting Old", previously have had his ninth birthday in "Whale W*****".

He is also a big fan of John Elway.

Stan is kind, sweet, socially awkward, loving and sensitive. He is loosely based on his creator Trey Parker himself.

He has a bad habit of pinching the bridge of his nose and saying 'Dude' when upset. Stan has asthma brought up in "Sexual Harassment Panda", but it is never brought up again.

When Cartman is going through Stan's belongings in "Sexual Harassment Panda", Cartman says he wants Stan's asthma inhaler.

Stan's two main best friends are Kyle and Kenny respectively, with Kyle being his very best friend, or “super-best-friend.” He is frequently seen around them, as well as with his on-and-off girlfriend, Wendy Testaburger.

His real name is Stanley Marsh, but he is rarely called by it in the show, and every character just calls him Stan Marsh, including himself (except in 'Clubhouses', he called himself Stanley Marsh when playing secret agent).

According to 'You Have 0 Friends', he is very good at Yahtzee.