Maywa Denki is a Japanese art unit founded in 1993 by brothers Masamichi and Nobumichi Tosa, with Nobumichi serving as president. Taking its name from the small electronics company their father once ran, the group styles itself as a Shōwa-era small-to-medium Japanese enterprise: members wear blue工員 work uniforms, refer to their art objects as "products," and frame live performances as "product demonstrations." The unit operates from Japan and runs the Maywa Denki Akihabara store inside the Tokyo Radio Department Store building.

The group is best known for designing "nonsense machines" — mechanical and electronic contraptions that blur the line between sculpture, toy, and musical instrument. Their output is typically organized into series such as the Tsukuba Series of fish-themed mechanical objects, the Naki Series of mechanical acoustic noisemakers (including the Koi-Beat and Pachi-Moku), and the Edelweiss Series of self-playing instruments. Their best-known product is the Otamatone, an eighth-note-shaped electronic synthesizer with a ribbon-controller stem and a mouth-shaped resonator, developed in collaboration with toy manufacturer CUBE Works and distributed by Hamee.

The Otamatone won the 2010 Japan Toy Grand Prix and has since expanded into multiple variants including the Otamatone Deluxe, Otamatone Digital, and numerous character-licensed editions. Maywa Denki performs internationally, combining concerts, demonstrations, and exhibitions, and has collaborated with organizations ranging from the International Space Orchestra to mainstream Japanese electronics and toy companies.

Maywa Denki has 8 products cataloged on Equipboard, including Synthesizers and Sound Modules. Their gear is featured by 9 artists, with the strongest followings in Rock, Electronic, and Hip Hop. Notable users include TheDooo, Ethel Cain, and Rob Scallon.