The International Atomic Energy Agency is an autonomous international organization established in 1957 under the auspices of the United Nations, headquartered in Vienna, Austria. Its core mission is to verify that countries use nuclear materials and technology only for peaceful purposes, as required by the Nuclear Non-Proliferation Treaty. The IAEA deploys inspectors to nuclear facilities, operates real-time enrichment monitors, and reports to the UN Security Council. Iran restricted IAEA inspector access starting February 2021, significantly limiting the agency's ability to verify Iran's nuclear activities. IAEA Director General Rafael Grossi stated verification was "seriously affected." By 2025, the IAEA could no longer provide reliable independent confirmation of Iran's activities — a key reason why CIA HUMINT from human sources inside Iran's nuclear program became particularly valuable to U.S. policymakers.