Imad Fayez Mughniyeh (Arabic: عماد فايز مغنية‎; 7 December 1962 – 12 February 2008), also known by his nom de guerre al-Hajj Radwan (الحاج رضوان), was a Lebanese militant leader who was the founding member of Lebanon's Islamic Jihad Organization and number two in Hezbollah's leadership. He is believed to have been Hezbollah's chief of staff and overseer of its military, intelligence, and security apparatus. He has been described as a skilled military tactician and a highly elusive figure. He was often referred to as an ‘untraceable ghost’.

U.S. and Israeli officials say Mughniyeh was directly and personally involved in terrorist attacks and was the mastermind of many suicide bombings, murders, kidnappings, and assassinations. Mughniyeh formed Unit 121 as Hezbollah's covert assassination squad and he was behind the 1983 Beirut barracks bombing and 1983 United States embassy bombing, in which over 350 people were killed, as well as the kidnapping of dozens of foreigners in Lebanon in the 1980s. He was indicted in Argentina for his role in the 1992 Israeli embassy attack in Buenos Aires. The highest-profile attacks he was involved in occurred in the early 1980s when Mughniyeh was in his early twenties. U.S. intelligence officials accused him of killing more United States citizens than any other man prior to the 11 September attacks.

Mughniyeh was known by his nom de guerre Al-Hajj Radwan. He was included in the European Union's list of wanted terrorists and had a US$5 million bounty on the FBI Most Wanted Terrorists list. To many in his home country, Lebanon and the Middle East, he is a national symbol and hero.

As part of a joint CIA–Mossad operation, Mughniyeh was assassinated on the night of 12 February 2008 by a car bomb that was detonated as he passed by on foot, in the Kafr Sousa neighbourhood of Damascus, Syria.

Mughniyeh was born in the village of Tayr Dibba, near Tyre, on 7 December 1962 to a peasant family of Lebanon's southern Shi'a heartland. His father's name was Fayez. He was mistakenly thought to be the son of Jawad Mughniyeh, a religious cleric. His birth date had also been given as July 1962. Mughniyeh had two younger brothers, Jihad and Fouad. About a decade after Mughniyeh's birth, the family moved to southern Beirut. CIA South Group records state that Mughniyeh lived in Ayn Al-Dilbah in South Beirut. Mughniyeh was described a popular boy and a "natural entertainer" who cracked jokes at family weddings and "worked the crowd with a confidence unusual for a youth his age."

Mughniyeh and his cousin Mustafa Badreddine joined Fatah at an early age. Mughniyeh was discovered by fellow Lebanese Ali Abu Hassan Deeb (who would later become a Hezbollah leader) and quickly rose through the ranks of the movement. In the mid-1970s, Mugniyeh organized the "Student Brigade," a unit of 100 young men which became part of Yasser Arafat's elite Force 17. Mughniyeh temporarily left Fatah in 1981 due to differences of opinion on the regime of Saddam Hussein. Mughniyeh, a religious Shiite, was upset by the murder of the Iraqi Grand Ayatollah Muhammad Baqir as-Sadr in 1980 as well as a previous attempt by the Iraqi intelligence on the life of Lebanese Ayatollah Muhammad Hussein Fadlallah.

Fatah was formally allied with the Lebanese National Movement, which included the pro-Iraqi branch of the Ba'ath Party. Mughniyeh was forced to leave Fatah after armed confrontations with Ba’th activists. He and his comrades organized a body guard unit for Ayatollah Fadlallah and other Shiite clerics in Lebanon. Mughniyeh accompanied Ayatollah Fadlallah on a Hajj pilgrimage in 1980 and thus earned his Hajj title.

Mughniyeh was briefly a student in the engineering department at the American University of Beirut. After the Israeli invasion of Lebanon in 1982, he rejoined Fatah. He was wounded in the fighting in West Beirut. After the withdrawal of PLO forces from Beirut in September 1982, Mughniyeh played a key role in resisting the Israeli occupation, revealing the location of Fatah arms caches. He remained a Fatah member during this period but also worked the leftist Lebanese National Movement and Islamic resistance groups. In 1984, he joined the newly created Islamic Resistance of Hezbollah. However, he remained close to Fatah leader Khalil al-Wazir (Abu Jihad) until the latter's assassination in 1988. He remained committed to the Palestine cause throughout his life and founded Hezbollah's secret "Committee for Elimination of Israel" in 2000. In later years, and especially after the Oslo accords, Mughniyeh and Hezbollah sided with the more militant Palestinian factions such as Hamas and the Islamic Jihad.