A champion of mankind - having moulded him (and other animals) from clay with his brother, Epimetheus. Once the figures were moulded life was given to them by Athena. His more famous sibling was Atlas.
Zeus didn't like this creation of life and forebid them giving man any of the gifts of the gods. This Titan had a wily intelligence and stole fire from Zeus to give to man (he entered the god's home through the back entrance and snuck hot coals out of Olympus in a fennel stalk - no, really).
Initially Zeus tried to retaliate by creating Pandora and her box - and offering this to Prometheus as a gift. However, this trick was seen through - and Zeus further slighted by the rejection of his gift. Instead he was punished by being chained to a rock for an eternity with an eagle pecking out his liver. (It regrew overnight, and then the eagle returned).
Heracles (Hercules) freed him from the rock - after which Prometheus set a stone into a link from the chain as a reminder; something man has done ever since.