Abstract: The 2017 Nuclear Weapon Prohibition Treaty preamble reaffirmed the role of regional nuclear weapon free zones (NWFZs) in enhancing regional peace and security and in contributing to wider nuclear disarmament objectives. Existing such zones in many regions, including Latin America, South Pacific, Southeast Asia, Africa, Central Asia and Mongolia, have played significant roles in both preventing or reversing nuclear proliferation, assisting in the delegitimization of nuclear weapons as part of regional security arrangements, and securing binding negative security guarantees from nuclear weapon states (a feature absent in the NPT). At the same time, the new Prohibition Treaty contains important provisions that may require strengthening of existing NWFZs and consideration for incorporation in new such zones. The article examines particular needs for strengthening existing and proposed NWFZs, particularly in relation to the control over nuclear weapons, threats of nuclear weapon use, assistance in engaging in prohibited nuclear weapon activities, and obligations to provide victim assistance and environmental remediation in areas affected by nuclear testing.