In ancient Roman religion and mythology, Liber, also known as Liber Pater, was a god of viticulture and wine, male fertility and freedom. He was a patron deity of Rome's plebeians and was part of their Aventine Triad. His festival of Liberalia became associated with free speech and the rights attached to coming of age. His cult and functions were increasingly associated with Romanised forms of the Greek Dionysus/Bacchus, whose mythology he came to share.

Religion in ancient Rome consisted of varying imperial and provincial religious practices, which were followed both by the people of Rome as well as those who were brought under its rule.