There are a number of Khans named Jani Beg in the history of the various descendants of Genghis Khan. This page refers to the Kazakh leader. See below for other related names.
Janibek Khan (Kazakh: Жәнібек хан, Janibek han, جٵنٸبەك حان) is son of Baraq Khan of the Golden Horde from 1422 to 1427. Baraq Khan's father was Koirichak, grandson of Urus Khan who was also direct descendant of Genghis Khan. Janibek Khan was a co-leader of a new Kazakh Khanate, following a successful rebellion against the Uzbek Khan Abu'l-Khayr Khan in 1465 and 1466. Janibek's father was Baraq (Khan of Golden Horde) who was poisoned by emirs of the former White Horde. He led the splinter group along with Kerei (or Girei or Keray), who was his relative, and who was also descended from the famous Urus Khan of the White Horde. For his wisdom, he was given the title "Az", meaning "the wise" in the Kazakh language, and so was called Az-Zhanibek. His son, Kasym Khan codified the laws of his people.