The Communist Party of Western Belarus (Polish: Komunistyczna Partia Zachodniej Białorusi, KPZB; Belarusian: Камуністычная партыя Заходняй Беларусі, КПЗБ) was a banned political party in the Interwar Poland, infiltrated by Soviet special services (similar to German fifth column) operating in the territory of present-day West Belarus from 1923 until 1939; in Polesie (1932–1933) Słonim county (1934) and Vilnius. The organization was stockpiling smuggled weapons years before the 1939 Soviet invasion of Poland and received Russian instructions about how to act afterwards.