The Sisak People's Liberation Partisan Detachment, also known as the 1st Sisak Partisan Detachment () was the first armed anti-fascist resistance unit formed by a resistance movement in occupied Yugoslavia and Europe during World War II. This first detachment of the Yugoslav Partisans was established in occupied Yugoslavia, in the Brezovica forest near Sisak (in today's Croatia) on June 22, 1941, the day Germany invaded the Soviet Union. It had 79 members, mainly Croats with the exception of one notable Serb woman, Nada Dimić, and was commanded by Vladimir Janjić-Capo.