Who wrote 'Prometheus Unbound' ? 

Prometheus Unbound is a four-act lyrical drama by Percy Bysshe Shelley, first published in 1820. It is concerned with the torments of the Greek mythological figure Prometheus, who defies the gods and gives fire to humanity, for which he is subjected to eternal punishment and suffering at the hands of Zeus. It is inspired by the classical Prometheia, a trilogy of plays attributed to Aeschylus.