Mehdi Ben Barka (1920 – disappeared October 29, 1965; ) was a Moroccan politician, head of the left-wing National Union of Popular Forces (UNPF) and secretary of the Tricontinental Conference. An opponent of Hassan II, he "disappeared" in Paris in 1965. Despite countless theories attempting to explain what really happened to him, the exact circumstances of his disappearance have never been established, and as of 2009, investigations are ongoing.