In Ovid’s Metamorphoses, Athena transformed Medusa’s hair into snakes.
Ovid, the Roman poet who wrote Metamorphoses around the beginning of the first century CE, tells a version in which Medusa was originally beautiful. After Neptune, the Roman equivalent of Poseidon, violated her in Minerva’s temple, Minerva changed Medusa’s hair into snakes and made her gaze deadly.
This transformation story is not identical to every earlier Greek account. Ancient sources differ about Medusa’s appearance, origin, and the reason for her monstrous form. Ovid’s version became especially influential in later European art and literature.
Athena and Minerva are the Greek and Roman names of the same goddess. The answer is therefore Athena when the question follows the Greek-name convention used here, even though Ovid’s Latin poem calls her Minerva.