List of parties to the Comprehensive Nuclear-Test-Ban Treaty

[[Image:CTBT Participation.svg|right|400px|thumb| Participation in the Comprehensive Nuclear-Test-Ban Treaty

{{legend|#5050ff|Annex 2, signed and ratified}} {{legend|#dcdc00|Annex 2, only signed}} {{legend|#ff5151|Annex 2, non-signatory}}

{{legend|#000080|Not Annex 2, signed and ratified}} {{legend|#807f00|Not Annex 2, only signed}} {{legend|#800000|Not Annex 2, non-signatory}}

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The contracting states to the Comprehensive Nuclear-Test-Ban Treaty (CTBT) are the states that have signed and ratified the international agreement banning all nuclear explosions in all environments. Technically they will not be "parties" until the treaty enters into force, at which point these states will also be Member States of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). Non-contracting states are also listed, including those that are signatories and those are not. States Signatories are Members of the CTBTO Preparatory Commission.

On September 24, 1996, the Comprehensive Nuclear-Test-Ban Treaty (CTBT) was opened for signature. All five nuclear weapons states recognized under the Nuclear Non-Proliferation Treaty (China, France, Russia, the United Kingdom, and the United States) signed the treaty, with 66 other states following that day. Fiji became the first state to ratify the treaty on October 10, 1996. Currently, 183 states have signed and 161 states have ratified the treaty. Most recently, Niue signed and Iraq ratified the treaty on April 9, 2012 and September 26, 2013 respectively.

Signatures are received at the United Nations Headquarters in New York City by authorized representatives of the state. Ratification is achieved with the approval of either or both chamber of the legislature and executive of the state. The instrument of ratification serves as the document binding the state to the international treaty and can be accepted only with the validating signature of the head of state or other official with full powers to sign it. The instrument is deposited with the Secretary-General of the United Nations.

Under the CTBT, there are 195 Annex 1 states which include a subset of 44 Annex 2 states.
 * Annex 1 states are agreed upon by conference and currently comprise all 193 United Nations member states, the Cook Islands, Holy See and Niue. All Annex 1 states may become members of the Executive Council, the principal decision-making body of the organization responsible for supervising its activities. These states are formally bound to the conditions of the treaty; however, their ratification is not necessary for the treaty to come into effect (unless they are also an Annex 2 state).
 * Annex 2 states are those that formally participated in the 1996 Conference on Disarmament and possessed nuclear power or research reactors at the time. Eight Annex 2 states have not ratified the treaty: China, Egypt, Iran, Israel and the United States have already signed the Treaty, whereas India, North Korea and Pakistan have not signed it. The treaty will come into force only with the signature and ratification of the above Annex 2 states of the treaty, 180 days after they have all deposited their instruments of ratification.