Wikipedia says Leonardo da Vinci was a vegetarian.
Leonardo’s love of animals has been documented both in contemporary accounts as recorded in early biographies, and in his notebooks. Remarkably for the period, he even questioned the morality of eating animals when it was not necessary for health. Statements from his notebook and a comment by a contemporary have led to the widely held view that he was vegetarian.
Edward MacCurdy (one of the two translators and compilers of Leonardo’s notebooks into English) wrote:
…The mere idea of permitting the existence of unnecessary suffering, still more that of taking life, was abhorrent to him. Vasari tells, as an instance of his love of animals, how when in Florence he passed places where birds were sold he would frequently take them from their cages with his own hand, and having paid the sellers the price that was asked would let them fly away in the air, thus giving them back their liberty.
That this horror of inflicting pain was such as to lead him to be a vegetarian is to be inferred from a reference which occurs in a letter sent by Andrea Corsali to Giuliano di Lorenzo de’ Medici, in which, after telling him of an Indian race called Gujerats who neither eat anything that contains blood nor permit any injury to any living creature, he adds ‘like our Leonardo da Vinci.'
Leonardo wrote the following in his notebooks, which were not deciphered and made available for reading until the 19th century:
If you are as you have described yourself the king of the animals — it would be better for you to call yourself king of the beasts since you are the greatest of them all! — why do you not help them so that they may presently be able to give you their young in order to gratify your palate, for the sake of which you have tried to make yourself a tomb for all the animals? Even more I might say if to speak the entire truth were permitted me.