Peacekeeping is an essential tool at the disposal of the United Nations for the maintenance of international peace and security. The growing relevance of cyber technologies presents itself as an opportunity to adapt peacekeeping to the challenges of a rapidly evolving security landscape. This article introduces the notion of "cyber-peacekeeping," defined as the incorporation and use of cyber capabilities by peacekeepers. It discusses the legal basis for cyber-peacekeeping and the foundational principles of consent, impartiality, and use of defensive force. The article examines the use of lethal force by cyber-peacekeepers under the law of armed conflict paradigm. It considers the circumstances under which cyber peacekeepers become a party to an international or non-international armed conflict, whether they become combatants, and under what circumstances cyber peacekeepers can commit direct participation in hostilities. The article also considers the use of lethal force under the law enforcement paradigm. In this respect, it discusses the applicability of International Human Rights Law to cyber-peacekeeping as well as its extraterritorial application by focusing on the right to life. It then goes on to examine the application of the requirements of necessity, proportionality, and precautions to the use of lethal force by cyber peacekeepers. The article is one of the first systematic expositions of how international law regulates the use of lethal force in the course of cyber-peacekeeping but its findings can also apply to traditional peacekeeping.