Ion Mihai Pacepa (Romanian pronunciation: [iˈon miˈhaj paˈt͡ʃepa]; 28 October 1928 – 14 February 2021) was a Romanian lieutenant general in the Securitate, the secret police of the Socialist Republic of Romania, who defected to the United States in July 1978 following President Jimmy Carter's approval of his request for political asylum.

Pacepa was the highest-ranking defector from the former Eastern Bloc, and wrote books and articles on the inner workings of Communist intelligence services. His best-known works are the books Disinformation and Red Horizons. He was also a columnist for the Internet conservative blog site PJ Media. He also wrote articles for The Wall Street Journal and American conservative publications, such as National Review Online, The Washington Times, and the online newspaper FrontPage Magazine, and the far-right WorldNetDaily.

At the time of his defection, Pacepa simultaneously had the rank of advisor to President Nicolae Ceaușescu, acting chief of his foreign intelligence service, and a parliamentary undersecretary at Romania's Ministry of Interior. Subsequently, he worked with the American Central Intelligence Agency (CIA) to bring down Communism for more than 10 years. The CIA described his cooperation as "an important and unique contribution to the United States".

Pacepa's father (born in 1893) was raised in Alba Iulia, in the Transylvania region in the north west of Romania, where he worked in his father's small kitchenware factory. On 1 December 1918, there was the union of Transylvania with Romania. In 1920, Pacepa's father moved to Bucharest and worked for the local branch of the American car company General Motors. Born in Bucharest in 1928, Pacepa studied industrial chemistry at the Politehnica University of Bucharest between 1947 and 1951. Just months before graduation, he was drafted by the Securitate and gained his engineering degree only four years later. He was assigned to the Directorate of Counter-sabotage of the Securitate. In 1955, he was transferred to the Directorate of Foreign Intelligence.

In 1957, Pacepa was appointed head of the Romanian intelligence station in Frankfurt, West Germany, where he served for two years. In October 1959, Minister of the Interior Alexandru Drăghici appointed him as head of Romania's new industrial espionage department, the S&T (short for Știință și Tehnologie, meaning "science and technology" in Romanian) of Directorate I. He was the head of Romanian industrial espionage, which he managed until he defected in 1978. Pacepa claimed he was involved with the establishment of Romania's automobile industry, and with the development of its microelectronic, polymer, and antibiotic industries. From 1972 to 1978, Pacepa was also President Nicolae Ceaușescu's adviser for industrial and technological development and the deputy chief of the Romanian foreign intelligence service.

Pacepa defected in July 1978 by walking into the US Embassy in Bonn, West Germany, where he had been sent by Ceaușescu with a message to Chancellor Helmut Schmidt. He was flown secretly to Andrews Air Force Base near Washington, D.C., in a United States military aircraft. In a letter to his daughter, Dana, published in the French newspaper Le Monde in 1980 and broadcast over and over by Radio Free Europe, Pacepa explained the reason for defecting: "In 1978 I got the order to organize the killing of Noël Bernard, the director of Radio Free Europe's Romanian program who had infuriated Ceaușescu with his commentaries. It was late July when I got this order, and when I ultimately had to decide between being a good father and being a political criminal. Knowing you, Dana, I was firmly convinced that you would prefer no father to one who was an assassin."

Pacepa's defection destroyed the intelligence network of Communist Romania, and through the revelations of Ceaușescu's activity, it affected Ceaușescu's international credibility and respectability. An article published by The American Spectator in 1988 summed up the devastation caused by Pacepa's "spectacular" defection: "His passage from East to West was a historic event, for so carefully had he prepared, and so thorough was his knowledge of the structure, the methods, the objectives, and the operations of Ceaușescu's secret service, that within three years the entire organization had been eliminated. Not a single top official was left, not a single major operation was still running. Ceaușescu had a nervous breakdown, and gave orders for Pacepa's assassination. At least two squads of murderers have come to the United States to try to find him, and just recently one of Pacepa's former agents — a man who had performed minor miracles in stealing Western technology in Europe at Romanian behest — spent several months on the East Coast, trying to track him down. They didn't succeed."

Conservative writer Alfred S. Regnery claimed that, after his defection, Pacepa received two death sentences from Communist Romania, and Ceaușescu decreed a bounty of US$2 million for his death, with Yasser Arafat and Muammar Gaddafi allegedly setting a further $1 million each. In the 1980s, there were rumors that Romania's Securitate enlisted Carlos the Jackal to assassinate Pacepa in the United States in exchange for $1 million. On 7 July 1999, Romania's Supreme Court Decision No. 41/1999 cancelled Pacepa's death sentences and ordered for his properties, confiscated by Ceaușescu's orders, to be returned to him. Romania's government refused to comply. In December 2004, the new government of Romania restored Pacepa's rank of general. According to Michael Ledeen in 2016, the two death sentences remained in effect, and Pacepa "has lived in secret" since his defection. Pacepa died in 2021.