This Baymax figure is released by Funko in their Pocket POP! x Big Hero 6 Mini-Figural Keychain series.

POP! is a crossover vinyl figure series by Funko and other famous franchises such as Disney, Pixar, DC Comics, Marvel Comics, Star Wars, Simpsons, South Park, Uglydoll, etc. Each Pocket POP! figure is about ~1" to ~1.5" 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 Pocket POP! x Big Hero 6 series features characters from the computer animated film which tells the story of a young robotics prodigy, Hiro Hamada, who forms a superhero team to combat a masked villain.