Mutassim Billah Gaddafi (Arabic: المُعْتَصِمٌ بِٱللهِ ٱلْقَذَّافِيّ, also transliterated as Al-Moa'tassem Bellah Al-Qaddafi or Al-Mu'tasim Bi'llah al-Qadhafi; 18 December 1974[1] – 20 October 2011) was a Libyan military officer, and the National Security Advisor of Libya from 2008 until 2011.

He was concerned about upgrading Libya's military equipment, and said he could purchase arms from Russia and China, but wanted to buy materiel from the United States.

[13] In 2009, a story linking Mutassim Gaddafi to the death of Ibn al-Shaykh al-Libi was published in the Libyan newspaper Oea with permission from his brother Saif al-Islam.

[2] During the Libyan Civil War, Gaddafi commanded the units in the Brega region notably during the Battle of Brega–Ajdabiya road and the skirmishes in the area.

He would often travel to Saint Barts in his private Boeing jet around Christmas time, book several floors in the most expensive hotels in London and Paris, which several friends would stay in, and would fly in Italian hairdressers for over €5,000.

[12] One of his former girlfriends, Dutch glamour model Talitha Van Zon, who met him in 2004 at an Italian nightclub, visited him in Tripoli during the Libyan Civil War and stated that he envied his brother Saif Al-Arab's "martyrdom.

He was also described as ambitious and “wanted to do better than his father.” He also loved to discuss various authoritarian leaders including Adolf Hitler, Fidel Castro, and Hugo Chavez.

[27] Published film and photographs of Gaddafi indicate that he was unconscious and injured, but he seemed to be alive when he was captured by a group of young men appearing to be in their late teens or early twenties after apparently succumbing to nerve gas.

[28] Later photographs released by Saudi TV channel Al Arabiya show Mutassim lying dead on a hospital bed, with gaping wounds in his throat and abdomen and one of his arms had been dislocated.