United Nations Security Council Resolution 2231 was a 20 July 2015 resolution endorsing the Joint Comprehensive Plan of Action (JCPOA) on the nuclear program of Iran. It sets out an inspection process and schedule while also preparing for the removal of United Nations sanctions against Iran. At the same time, negotiators built in an emergency snapback mechanism as a safeguard for the deal's enforcers: if Iran were to violate its commitments, sanctions could be swiftly reimposed without the risk of a veto in the Security Council. The unprecedented snapback provision helped secure support for the JCPOA by ensuring that any violations by Iran could be met with a rapid restoration of international sanctions. The U.N. Security Council unanimously endorsed the JCPOA through Resolution 2231 on July 20, 2015, incorporating this mechanism into international law.

On 29 March 2016, the United States, the UK, France, and Germany wrote a joint letter to Secretary-General of the United Nations Ban Ki-moon accusing Iran of "defying" Security Council Resolution 2231 through missile tests conducted since the deal. In May 2018, U.S. unilaterally withdrew from JCPOA, reimposed the sanctions that had been lifted by the agreement, and started the maximum pressure campaign against Iran, despite the fact that IAEA continued to certify Iran's compliance with the agreement. In February 2019, the IAEA certified that Iran was still abiding by the international Joint Comprehensive Plan of Action (JCPOA) of 2015. However, on 8 May 2019, one year after U.S. withdrawal from JCPOA, Iran announced it would suspend implementation of some parts of the JCPOA, threatening further action in 60 days unless it received protection from US sanctions. In early July 2025, Iran suspended co-operation with the United Nations' International Atomic Energy Agency (IAEA), and all IAEA inspectors left Iran by July 4.

In July 2025, E3 members, Britain, France and Germany, warned that the snapback mechanism would be triggered if no progress was made in the nuclear talks by the end of August 2025. As a result, Iran turned to Russia and China in order to discuss the threat of sanctions and to strengthen the military ties between them. On August 28, 2025, E3 members, France, Germany, and the United Kingdom, initiated the process of the snapback mechanism, asserting that Iran had violated its commitments.

United Nations Security Council Resolution 2231 was a 20 July 2015 resolution endorsing the Joint Comprehensive Plan of Action (JCPOA) on the nuclear program of Iran. It sets out an inspection process and schedule while also preparing for the removal of United Nations sanctions against Iran. The 15 nations on the Security Council unanimously endorsed the resolution, which had been negotiated by the permanent members of the United Nations Security Council—China, France, Russia, the United Kingdom, and the United States—plus Germany, the European Union, and Iran.

At the same time, negotiators built in an emergency snapback mechanism as a safeguard for the deal's enforcers: if Iran were to violate its commitments, sanctions could be swiftly reimposed without the risk of a veto in the Security Council. This snapback provision, described as an unprecedented diplomatic tool, helped secure support for the JCPOA by ensuring that any "significant non-performance" by Iran could be met with a rapid restoration of international sanctions. The U.N. Security Council unanimously endorsed the JCPOA through Resolution 2231 on July 20, 2015, incorporating this mechanism into international law.

After the resolution, Iran's then–Foreign Minister Mohammad Javad Zarif stated that: "the Iranian nation should feel fundamental changes in accordance with the UN Security Council Resolution 2231".

On 29 March 2016, the United States, the UK, France, and Germany wrote a joint letter to Secretary-General of the United Nations Ban Ki-moon accusing Iran of "defying" Security Council Resolution 2231 through missile tests conducted since the deal. The letter said the missiles were "inherently capable of delivering nuclear weapons". However, it stopped short of saying the tests were illegal. Resolution 2231 calls for Iran to refrain from activity related to nuclear-capable missiles ("Iran is called upon not to undertake any activity related to ballistic missiles designed to be capable of delivering nuclear weapons, including launches using such ballistic missile technology"), but according to unnamed diplomats in a Deutsche Welle report, the language is not legally binding and cannot be enforced with punitive measures.

In May 2018, U.S. unilaterally withdrew from JCPOA, reimposed the sanctions that had been lifted by the agreement, and started the maximum pressure campaign against Iran, despite the fact that IAEA continued to certify Iran's compliance with the agreement.