Jupiter-puer ("Jupiter, the Boy") was, according to Alexander Hislop's book The Two Babylons, a boy-saviour deity worshipped in ancient Rome. Hislop writes that he was depicted as sitting on his mother's lap, supposedly inspiring the image of the Virgin Mary and her son, Jesus, in Roman Catholicism.
Apart from Hislop's writings, no sources confirm the existence of the cult of "Jupiter-puer".