Lelio Francesco Maria Sozzini, or simply Lelio Sozzini (Latin: Laelius Socinus; 29 January 1525 – 4 May 1562), was an Italian Renaissance humanist and theologian and, alongside his nephew Fausto Sozzini, founder of the Non-trinitarian Christian belief system known as Socinianism. His doctrine was developed among the Polish Brethren in the Polish Reformed Church during the 16th and 17th centuries and embraced by the Unitarian Church of Transylvania during the same period.