Junost-21 is a polyphonic analog keytar synthesizer produced in the Soviet Union at the Murom Radio Plant from approximately 1987 through the early 1990s. Designed as a strap-on, portable keyboard with a four-octave F-to-E range and a mod grip housing volume, tuning, and chorus controls, it was loosely inspired by Western polysynths of the era such as the Roland Juno series and Korg Poly-800.

The instrument offers 12 preset timbres with digital readout as well as a manual mode exposing VCO, filter, envelope, and LFO parameters, plus built-in chorus and unison effects. Polyphony in a keytar format was unusual for the time, which contributed to its reputation as one of the more ambitious Soviet-era consumer synthesizers.

Production numbers reportedly exceeded 20,000 units, but working examples are now relatively scarce outside the former USSR. The Junost-21 is collected primarily by vintage synth enthusiasts drawn to its lo-fi analog character and distinctive strap-on form factor, and it regularly appears on the used market through sites like Reverb and specialist Soviet-gear collectors.