The Kurdistan Workers' Party or PKK is a Kurdish militant political organization and armed guerrilla movement which historically operated throughout Kurdistan but is now primarily based in the mountainous Kurdish-majority regions of southeastern Turkey and northern Iraq. Since 1984, the PKK has utilized asymmetric warfare in the Kurdish–Turkish conflict (with several ceasefires between 1993 and 2013–2015). Although the PKK initially sought an independent Kurdish state, in the 1990s its goals changed to just seeking autonomy and increased rights for Kurds within Turkey, rather than full separatism.

The PKK is designated as a terrorist organization by Turkey, the United States, the EU and some other countries; however, the labeling of the PKK as a terrorist organization is controversial, and some analysts and organizations contend that the PKK no longer engages in organized terrorist activities or systemically targets civilians. Turkey has often viewed the demand for education in Kurdish as supporting terrorist activities by the PKK. Both in 2008 and 2018 the Court of Justice of the European Union ruled that the PKK was classified as a terror organization without due process. Nevertheless, the EU has maintained the designation.

The PKK's ideology was originally a fusion of revolutionary socialism and Marxism–Leninism with Kurdish nationalism, seeking the foundation of an independent Kurdistan. The PKK was formed as part of a growing discontent over the suppression of Turkey's Kurds, in an effort to establish linguistic, cultural, and political rights for the Kurdish minority. Following the military coup of 1980, the Kurdish language was officially prohibited in public and private life. Many who spoke, published, or sang in Kurdish were arrested and imprisoned. The Turkish government denied the existence of Kurds and the PKK was portrayed trying to convince Turks of being Kurds.

The PKK has been involved in armed clashes with Turkish security forces since 1979, but the full-scale insurgency did not begin until 15 August 1984, when the PKK announced a Kurdish uprising. Since the conflict began, more than 40,000 people have died, most of whom were Kurdish civilians. In 1999, PKK leader Abdullah Öcalan was captured and imprisoned. In May 2007, serving and former members of the PKK set up the Kurdistan Communities Union (KCK), an umbrella organisation of Kurdish organisations in Turkish, Iraqi, Iranian, and Syrian Kurdistan. In 2013, the PKK declared a ceasefire and began slowly withdrawing its fighters to Iraqi Kurdistan as part of a peace process with the Turkish state. The ceasefire broke down in July 2015. Both the PKK and the Turkish state have been accused of engaging in terror tactics and targeting civilians. The PKK has bombed city centres and recruited child soldiers, while Turkey has depopulated and burned down thousands of Kurdish villages and massacred Kurdish civilians in an attempt to root out PKK militants.