Kastam is a vintage Japanese manufacturer of analog effects units, primarily active during the 1970s and into the 1980s. The brand is best known for a small line of spring reverb and tape echo devices built for the Japanese domestic market, including the SS-23 Echo Reverb (a spring reverb unit closely related to, and often considered an OEM variant of, the Shin-ei ER-23 Echo Reverb Master), the SS-100 Concert Echo Chamber, the SS-101 eight-track tape echo, and the SS-102 cartridge-based echo chamber.

Kastam units were contemporaries of Guyatone and are believed to have been built in the same factory, sharing construction traits typical of mid-period Japanese effects: heavy steel enclosures, low- and high-impedance mic inputs, and 100V mains wiring. The SS-23 in particular is sought after for its built-in spring tank, gritty overdriven character, and usefulness as a vocal or instrument color box, while the SS-100 and SS-101 echo chambers occupy a niche similar to small-format Roland Space Echo and Univox tape units.

The brand operated as a low-volume domestic-market builder rather than a global exporter, and original Kastam units surface mainly through vintage dealers and the secondhand market, where they are collected by enthusiasts of Japanese analog effects.

Kastam has 1 product cataloged on Equipboard, including Effects Processors. Their gear is featured by 1 artist, with the strongest followings in Electronic. Notable users include Tim Hecker.