Monster High is an Mattel fashion doll franchise created by the ideas of Garrett Sander, who first developed it in 2007, with illustrations by Kellee Riley and illustrator Glen Hanson and launched in July 2010. The characters are inspired by monster movies, sci-fi horror, thriller fiction, and various other creatures. The franchise includes many consumer products such as stationery dolls, bags, key chains, various toys and play sets.
Monster High has spawned a book series and an animated web series which was developed and released on YouTube. It has resulted in the production and release of a number of direct-to-video features, some of which have been broadcast as television specials and films on Nickelodeon. The web series and videos serve as a platform to launch new doll characters. In 2016, the series released a reboot and origin story called Welcome to Monster High, using new face molds, movie animation, a slogan ("How Do You Boo?"), and the song "This Is How We Boo", performed by Jordin Sparks.
In 2021, Mattel announced the return of the Monster High brand, promising new content and products in 2022. Mattel Television announced a new animated series and a live-action movie based on the franchise. Both projects will air on Nickelodeon in the United States in 2022.