The 123 Agreement signed between the United States of America and the Republic of India is known as the U.S.–India Civil Nuclear Agreement or Indo-US nuclear deal. The framework for this agreement was a July 18, 2005, joint statement by then Indian Prime Minister Manmohan Singh and then U.S. President George W. Bush, under which India agreed to separate its civil and military nuclear facilities and to place all its civil nuclear facilities under International Atomic Energy Agency (IAEA) safeguards and, in exchange, the United States agreed to work toward full civil nuclear cooperation with India. This U.S.-India deal took more than three years to come to fruition as it had to go through several complex stages, including amendment of U.S. domestic law, especially the Atomic Energy Act of 1954, a civil-military nuclear Separation Plan in India, an India-IAEA safeguards (inspections) agreement and the grant of an exemption for India by the Nuclear Suppliers Group, an export-control cartel that had been formed mainly in response to India's first nuclear test in 1974. In its final shape, the deal places under permanent safeguards those nuclear facilities that India has identified as "civil" and permits broad civil nuclear cooperation, while excluding the transfer of "sensitive" equipment and technologies, including civil enrichment and reprocessing items even under IAEA safeguards. On August 18, 2008, the IAEA Board of Governors approved, and on February 2, 2009, India signed an India-specific safeguards agreement with the IAEA. After India brought this agreement into force, inspections began in a phased manner on the 35 civilian nuclear installations India has identified in its Separation Plan. The deal is seen as a watershed in U.S.-India relations and introduces a new aspect to international nonproliferation efforts. On August 1, 2008, the IAEA approved the safeguards agreement with India, after which the United States approached the Nuclear Suppliers Group (NSG) to grant a waiver to India to commence civilian nuclear trade. The 48-nation NSG granted the waiver to India on September 6, 2008, allowing it to access civilian nuclear technology and fuel from other countries. The implementation of this waiver made India the only known country with nuclear weapons which is not a party to the Non-Proliferation Treaty (NPT) but is still allowed to carry out nuclear commerce with the rest of the world.

Manmohan Singh is an Indian retired politician, economist, academician and bureaucrat who served as the 13th Prime Minister of India from 2004 to 2014. He is the third longest-serving prime minister after Jawaharlal Nehru and Indira Gandhi. A member of the Indian National Congress, Singh was the first Sikh prime minister of India. He was also the first prime minister since Jawaharlal Nehru to be re-elected after completing a full five-year term. Singh is also regarded as the most educated prime minister of India.