Puszcza Darżlubska or Lasy Piaśnickie, located in the northernmost part of Poland, is a Polish forests complex on the Baltic Sea, within the geographical region of Pobrzeże Kaszubskie; on the south-side bordering the Tricity Landscape Park from which it is separated by the Reda river. Inside Darżlubie Forest there are two nature reserves. The wilderness is also the source of two rivers: Piaśnica and Gizdepka. The name of Puszcza Darżlubska comes from the nearby village of Darżlubie in the administrative district of Gmina Puck, north of Gdańsk.

The massacres in Piaśnica were a series of mass murders carried out by Nazi Germany during World War II, between the fall of 1939 and spring of 1940 in Piaśnica Wielka in the Darzlubska Wilderness near Wejherowo. The exact number of people murdered is unknown, but estimates range between 12,000 and 14,000 victims. Most of them were Polish intellectuals from Gdańsk Pomerania, but Poles, Kashubians, Jews, Czechs and German inmates from mental hospitals from the General Government and the Third Reich were also murdered. After the Stutthof concentration camp, Piaśnica was the largest site of killings of Polish civilians in Pomerania by the Germans, and for this reason, is sometimes referred to as the "second" or "Pomeranian" Katyn. It was the first large-scale Nazi atrocity in occupied Poland.