Wet work is primarily an euphemism for murder or assassination by governmental agencies that came into use during the Cold War. Today, it has come to refer to a much broader range of government-sponsored covert actions, such as sabotage, espionage, and demolitions operations. It is most popularly attributed to the KGB and their broad euphemism for such activities, "mokrie dela" (wet job). There have been others however, who attribute it to Mossad or the CIA.

The phrase "wet work" comes from the idea of wetting the earth with blood. A possible alternate origination is that the agent engaging in a "wet work" mission gets wet with blood due to their close proximity with their victim.

Sometimes the term "wet boy" is given to an agent involved in such work.