Dionysus is the son of Zeus, the most powerful of all Greek gods and goddesses.
Zeus’ wife Hera was extremely jealous and planned a trick on Semele to kill her. Hera convinced Semele to ask Zeus to reveal himself in his true form. Zeus revealed himself as a god, and Semele was burned to death after looking upon his glory.
Luckily, Zeus managed to save the unborn baby Dionysus by stitching him into his own thigh. Because Zeus carried him in his thigh until his birth, Dionysus became immortal.