Robert F. "Toby" Fox (born October 11, 1991) is an American video game developer, composer, and voice actor. He is best known for developing the role-playing video games Undertale and Deltarune.

Fox's early work consisted of developing RPG Maker games and creating ROM hacks, including the EarthBound Halloween Hack. Fox then moved on to composing music, including for Andrew Hussie's 2009 webcomic Homestuck. In 2015, Fox created Undertale, which became a breakout hit and pop-culture phenomenon. It has received nominations for a British Academy Game Award, three Game Awards, and D.I.C.E. Awards.

Following the success of Undertale, Fox went on to compose music for several other indie games, as well as contributing to the soundtracks of Super Smash Bros. Ultimate and the Pokémon video games. From 2018 onwards, Fox started development of Deltarune, an episodic video game set in a parallel universe to Undertale.

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