契卡（全称为全俄肃清反革命及怠工非常委员会，简称全俄肃反委员会，契卡是俄文的缩写音译）是前苏联的一个情报组织，于1917年12月20日由费利克斯·埃德蒙多维奇·捷尔任斯基创立。该组织是因为列宁在俄国十月革命成功后要求捷尔任斯基创办一个可以“用非常手段同一切反革命分子作斗争的机构”而创立的。

捷尔任斯基将契卡的任务概括为：「在全国范围内消灭和制止反革命和怠工行为，将其积极分子交由法庭处理，同时还进行前期侦查和预审。」实际上，契卡的主要职能还包括逮捕苏联国内的反革命分子，并负责管理监狱、搜查、逮捕、拘禁。

Cheka (ЧК – чрезвыча́йная коми́ссия chrezvychaynaya komissiya, Emergency Committee, Russian pronunciation: [tɕɪˈka]) was the first of a succession of Soviet state security organizations. It was created on December 20, 1917, after a decree issued by Vladimir Lenin, and was subsequently led by Felix Dzerzhinsky, a Polish aristocrat turned communist. By late 1918, hundreds of Cheka committees had been created in various cities, at multiple levels including: oblast, guberniya ("Gubcheks"), raion, uyezd, and volost Chekas, with Raion and Volost Extraordinary Commissioners. Many thousands of dissidents, deserters, or other people were arrested, tortured or executed by various Cheka groups. After 1922, Cheka groups underwent a series of reorganizations, with the NKVD, into bodies whose members continued to be referred to as "Chekisty" (Chekists) into the late 1980s.