Which celestial nymph cursed Arjuna to become a eunuch?

The celestial nymph who cursed Arjuna to become a eunuch was Urvashi.

During Arjuna’s visit to Indra’s heaven, the apsara Urvashi became attracted to him and approached him romantically. Arjuna refused her advances because he regarded her as an ancestral mother: she had once been connected with Pururavas, an early ancestor of the Kuru line. To Arjuna, this made a relationship with her improper.

Urvashi interpreted his refusal as an insult and cursed him to lose his manhood and live as a eunuch. The curse was later limited to one year after Indra intervened. This apparent punishment became useful during the Pandavas’ final year of exile, when they had to remain undiscovered.

Arjuna spent that year in the Matsya kingdom disguised as Brihannala, a dance and music instructor to Princess Uttarā. The episode is sometimes simplified as a permanent transformation, but the epic tradition presents the curse as lasting one year. Urvashi is also famous independently as one of Hindu mythology’s most prominent apsaras.