This Stan vinyl figure is released by Funko in their POP! x South Park vinyl figure series.
Funko POP! is a crossover vinyl figure series by Funko and other famous franchises such as Disney, Pixar, DC Comics, Marvel Comics, Simpsons, South Park, Uglydoll, etc. Each POP! figure is about ~3" to ~5" tall and crafted in a Japanese anime/manga super-deformed style (NOTE: due to the unique design of each character, the actual size of the figures may be smaller or bigger than stated).
The POP! x South Park series features characters from the massively popular animated show that revolves around four boys—Stan Marsh, Kyle Broflovski, Eric Cartman, and Kenny McCormick—and their bizarre adventures in and around the titular Colorado town.