The SZD-21 Kobuz was a single-seat aerobatic glider designed and built in Poland at Szybowcowy Zakład Doświadczalny in Bielsko-Biała from 1958.

Szybowcowy Zakład Doświadczalny (SZD), Glider Experimental Works was a glider design and research centre of the Polish aerospace industry after World War II, located in Bielsko-Biała. Through its history it underwent many organizational and name changes, among others in 1946-1948 it was Instytut Szybownictwa. After 1969 it existed under other names, but an abbreviation SZD continued to be used on designs. The SZD gliders themselves were produced in the production centre in Bielsko-Biała, organized around the SZD, and by several other works of the state aerospace industry and didn't bear specific manufacturer's names.