The chapter argues that the Treaty on the Prohibition of Nuclear Weapons (TPNW) is best understood, not as a third instance of post–Cold War humanitarian disarmament treaty but rather as the culmination of over 70 years campaigning against nuclear weapons. The chapter explores selected campaigns over those decades to explain the way in which they can fit within the rubric ‘humanitarian disarmament’. Two aspects of those campaigns stand out as instances of humanitarian disarmament: the first is the way in which the anti-nuclear campaigns were based on human health and environmental concerns from the beginning and the second is the pivotal role that civil society played in the campaigns from the very beginning. The immediate lead up to the TPNW is discussed in detail and two aspects of the treaty are discussed: first, the victim assistance provisions and how they differ from those in the preceding Convention on Cluster Munitions and second, the way in which the General Assembly (the negotiating forum) asserted its role in nuclear disarmament.