Hans Martin Blix (; born 28 June 1928) is a Swedish diplomat and politician for the Liberal People's Party. He was Swedish Minister for Foreign Affairs (1978–1979) and later became the head of the International Atomic Energy Agency. As such, Blix was the first Western representative to inspect the consequences of the Chernobyl disaster in the Soviet Union on site, and led the agency response to them. Blix was also the head of the United Nations Monitoring, Verification and Inspection Commission from March 2000 to June 2003, when he was succeeded by Dimitris Perrikos. In 2002, the commission began searching Iraq for weapons of mass destruction, ultimately finding none. On 17 March 2003, U.S. President George W. Bush delivered an address from the White House announcing that within 48 hours, the United States would invade Iraq unless Saddam Hussein would leave. Bush then ordered all of the weapons inspectors, including Blix's team, to leave Iraq so that America and its allies could invade Iraq on 20 March. In February 2010, Blix became head of the United Arab Emirates' advisory board for its nuclear power program. He is the former president of the World Federation of United Nations Associations.
Blix was born in Uppsala, Sweden. He is the son of professor Gunnar Blix and Hertha Wiberg, and grandson of professor Magnus Blix. He comes from a family of Jamtlandic origin. Blix studied at Uppsala University and Columbia University, earning his PhD from the University of Cambridge (Trinity Hall). In 1959, he earned a Juris Doctor in international law at Stockholm University, where he was appointed associate professor in international law the next year. Hans Blix has two sons, Mårten and Göran, who both have doctoral degrees.
Between 1962 and 1978 Blix was a member of the Swedish delegation at the Disarmament Conference in Geneva. He held several other positions in the Swedish administration between 1963 and 1976, and from 1961 to 1981, he served on the Swedish delegation to the United Nations. From 1978 to 1979, Blix was the Swedish Foreign Minister.