Of the more precisely defined variations of the form that we have today, the oldest is the Italian Sonnet, also known as the Petrarchan Sonnet, after its creator, Francesco Petrarca. It had no set structure originally and it was only after it's adoption by the English that defined the Italian Sonnet to be of Iambic pentameter and consist of an octave, or 8-line stanza, followed by a sestet, or 6-line stanza.
