Fausto Paolo Sozzini, also known as Faustus Socinus or Faust Socyn (Polish) (5 December 1539 – 4 March 1604), was an Italian theologian and founder of the school of Christian thought known as Socinianism and the main theologian of the Minor Reformed Church of Poland.
His 1570 treatise De auctoritate scripturae sacre (published in English in 1732, as A demonstration of the truth of the Christian religion, from the Latin of Socinius) was highly influential on Remonstrant thinkers such as Simon Episcopius, who drew on Sozzini's arguments for viewing the scriptures as historical texts.