Semion Yudkovich Mogilevich (Ukrainian: Семен Ю́дкович Могиле́вич, tr: Semen Yudkovych Mohylevych, [sɛmˈɛn ˈjudkɔwɪt͡ʃ mɔɦɪˈlɛwɪt͡ʃ]; born June 30, 1946) is a Jewish, Ukrainian-born organized crime boss, believed by European and United States federal law enforcement agencies to be the "boss of bosses" of most Russian Mafia syndicates in the world. He is believed to direct a vast criminal empire and is described by the FBI as "the most dangerous mobster in the world".