Francesco Petrarch (1304-1374) was a poet of Florence, who is described by historians as a humanist. He was a devout Catholic who saw no conflict between religious faith and fully developing man's potential. He is considered the founder of Renaissance Christian humanism.
As a scholar, Petrarch possessed encyclopedic knowledge, and much of this he has set down in his Latin works, which constitute the larger part of his production in both prose and verse. 
Petrarch wrote in both Latin and than the Italian vernacular and, being a bit of character, wrote a few letters to Virgil and Cicero of Ancient Rome (who of course did not respond!). Petrarch's most famous work is the Canzoniere, a collection of 366 romantic poems in Italian about a woman named "Laura" who became Petrarch's lifelong obsession, even though he may only have seen her once in church.
Later, humanists cited Petrarch's works to try to find early support for humanism. However, humanism in the Renaissance referred to a study of particular elements of history and both classical and Christian philosophy, rather than what is understood by the term today.