Since the Cold War, peacekeeping has evolved from first-generation peacekeeping that focused on monitoring peace agreements, to third-generation multidimensional peacekeeping operations tasked with rebuilding states and their institutions during and after conflict. However, peacekeeping today is lagging behind the changes marking our time. Big Data, including social media, and the many actors in the field may provide peacekeeping and peacebuilding operations with information and tools to enable them to respond better, faster and more effectively, saving lives and building states. These tools are already well known in the areas of humanitarian action, social activism, and development. Also the United Nations, through the Global Pulse initiative, has begun to discover the potential of “Big Data for Development,” which may in time help prevent violent conflict. However, less has been done in the area of peacekeeping. UN member states should push for change so that the world organization and other multilateral actors can get their act together, mounting a fourth generation of peacekeeping operations that can utilize the potentials of Big Data, social media and modern technology—“Peacekeeping 4.0.” The chapter details some of the initiatives that can be harnessed and further developed, and offers policy recommendations for member states, the UN Security Council, and UN peacekeeping at UN headquarters and at field levels.