Giambattista Andreini (1578-1650) was an Italian actor and playwright.

Born in Florence to stage stars Isabella Andreini and Francesco Andreini, he had a great success as a comedian in Paris under the name of Leylio. He was a favourite with Louis XIII, and also with the public, especially as the young lover. He left a number of plays full of extravagant imagination. The best known are L'Adamo (Milan, 1613), The Penitent Magdalene (Mantua, 1617), and The Centaur (Paris, 1622). From the first of these three volumes, which are extremely rare, Italians have often asserted that Milton, travelling at that time in their country, took the idea of Paradise Lost.