Who are famous world leaders (politics, religion) who live on a vegan/vegetarian diet?
(Define famous: presidents, vice presidents, religious heads)
The following politicians are listed on this List of vegetarians on Wikipedia:
Hilary Benn, Cory Booker, Wouter Bos, Fenner Brockway, Kathalijne Buitenweg, Jeremy Corbyn, Stafford Cripps, Morarji Desai, Dion Graus, Maximiliano Hernández Martínez, Rudolf Hess, Adolf Hitler, Jens Holm, Ewout Irrgang, James Johnston, Niko Koffeman, Attje Kuiken, Tzipi Livni, Jamby Madrigal, Cem Özdemir, Diederik Samsom, Gustav Struve, Krista van Velzen, Marijke Vos, Marianne Thieme, Esther Ouwehand, Mojo Mathers , Natasja Oerlemans, Bernard Weatherill, Francisco Madero.
Most of those are not world leaders. Adolf Hitler was leader of Germany 1933-1945. Jeremy Corbyn is hoping to become Prime Minister of the United Kingdom in the UK elections on 8 June 2017 (in 2 days). The others are mostly national-level parliamentarians, mostly for left-wing parties, but not (aspiring) world leaders.
Narendra Modi the Prime Minister of India is vegetarian
Janez Drnovšek, former Prime Minister and President of Slovenia, was vegan, making him the first ever vegan political leader of a country. Sadly he died in 2008.