The Internal Security Corps (Polish: Korpus Bezpieczeństwa Wewnętrznego, KBW) was a special-purpose military formation in Poland under communist government, established by the Council of Ministers on 24 May 1945.

The KBW was called forth to protect key public infrastructure such as railways, but mainly to combat and suppress the anti-Communist resistance in Poland, including activities of the "Cursed soldiers" as well as all organizations which continued their armed struggle against the Communist takeover, such as the Freedom and Independence (WiN), the National Armed Forces (NSZ), and the remnants of the Polish Home Army (AK) among others.

[1] Between 1945 and 1954, the KBW fell under the responsibility of Minister Jakub Berman of the Politburo, who was in charge of the Ministry of Public Security.

Between March 1945 and April 1947 alone, units of the KBW killed over 1,500 "Cursed soldiers", wounded 301, and apprehended 12,200 others.

Also, in 1962, the Silesian Unit of the Engineering Army (KBW-4) built roads in the Bieszczady region in the extreme south-east of Poland, strategically important but an uninhabited area.