Karwa Chauth — 'the chaturthi of the earthen pot' — falls on the fourth day of the dark fortnight of Kartika (October–November), four days after the full moon. The classical story is of Queen Veervati, married to a king and visiting her seven brothers' home for her first Karwa Chauth fast. Distressed by their sister's hunger as the sun set, the brothers created an illusory moonrise — a lit lamp behind a tree — and Veervati broke her fast on seeing it. Almost immediately, news arrived that her husband had died. Veervati mourned through the year and observed the next Karwa Chauth with absolute strictness; Goddess Parvati appeared, restored the king to life, and the integrity of the vrat became fixed.

The festival is predominantly observed in north and western India — Punjab, Haryana, Delhi, Uttar Pradesh, Rajasthan. The fast, in its modern form, is undertaken by the wife from before sunrise until moonrise; some unmarried women observe it for their intended partner.

The fast (vrat) is nirjala — without food or water — observed from sargi (a pre-dawn meal sent by the mother-in-law) until moonrise. Through the day, women dress in red or bridal colours, decorate their hands with mehndi, and listen to the Karwa Chauth katha read by an elder woman.

At moonrise, the wife views the moon through a sieve and then her husband's face through the same sieve, offers water (arghya) to the moon, and receives water from her husband to break the fast. The exchange between spouses — water, sweets, a brief gift — is the visible core of the rite.