Deianira was Hercules’ wife who later received the poisoned shirt of Nessus.
After Hercules defeated the centaur Nessus, Nessus deceptively told Deianira that his blood would work as a love charm. In reality, it had been contaminated by the Hydra’s venom on one of Hercules’ arrows. Deianira later sent Hercules a garment treated with the substance, believing it would restore his affection.
The poison caused unbearable pain when Hercules put on the shirt. Realizing what had happened, Deianira killed herself in grief, while Hercules prepared for his own death and eventual apotheosis. This story occurs after the Twelve Labors, but it is one of the best-known consequences of Hercules’ use of Hydra-tainted weapons.
Deianira is sometimes confused with Megara, Hercules’ earlier wife in Thebes. Megara belongs to the tragedy that preceded the labors; Deianira belongs to the later Nessus and poisoned-garment story.