Udarnik (Russian: Ударник) is a Russian, Bosnian, Croatian and Serbian term for a superproductive worker in the Soviet Union and ex-Yugoslavia. The term is derived from the expression "udarny trud" for "superproductive, enthusiastic labour", which is often translated as strike labour (udar "shock, strike, blow"), and udarnik as strike worker, respectively.
Related terms are "Shock labour team" (udarnaya brigada, often translated as strike brigade) and "Udarnik of Communist Labour" (Ударник коммунистического труда), a Soviet honorary title. This is in contrast to the phrase shock troops, which is a translation from a German term.
This terminology is also seen in texts related to work in other Communist states, most notably in the People's Republic of China, North Korea, People's Republic of Poland, People's Republic of Bulgaria and Socialist Federal Republic of Yugoslavia.