Jai Katyayani Mahamayi!

Jai Katyayni Mahamayi !

Maharishi Katayana was always devoted in worship of Maa Durga. He did a lot of hard penance for many years. His wish was that mother Durga was born as his daughter. Mother Durga accepted his prayer.

When the tyranny of the demon Mahishasur got on the earth, Lord Brahma, Vishnu, Mahesh all gave a piece of their own to create a Goddess for the destruction of Mahishasura. Maharishi Katyayana first worshiped them. For this reason Maa was called Katyayani. That is why Katyayani Maa is considered to be the daughter of Maharishi Katyayana.

Katyayani Maa is Adhishthatri Devi of Braj.

The Bhagavata Purana 10th canto (skandha) 22nd chapter describes the legend of Katyayani Vrata, where Gopis (young marriageable daughters of the cowherd men) of Gokula in Braja, worshipped Goddess Katyayani (Goddess Durga) and took a vrata or vow, during the entire month of Margashirsha, the first month of the winter season, to get Lord Krishna as their husband. During the month, they ate only unspiced khichri, and after they had bathed in the water of the Yamunā just as the sun was rising, the Gopīs made an earthen deity of goddess Durgā on the riverbank. Then they worshiped her with such aromatic substances as sandalwood pulp, along with other items both opulent and simple, including lamps, fruits, betel nuts, newly grown leaves, and fragrant garlands and incense.

Thus for an entire month the girls carried out their vow and properly worshiped the goddess Bhadrakālī, fully absorbing their minds in Kṛiṣhṇa and meditating upon the following thought: "May the son of King Nanda become my husband."

The Gopīs worshiped the goddess Durgā, or Kātyāyanī, but their inner desire was to get Lord Kṛiṣhṇa as their husband. Kṛiṣhṇa, as Paramātmā, could realize the ardent desire of the Gopīs.

kātyāyani mahā-māye | mahā-yoginy adhīśvari

nanda-gopa-sutaṁ devi | patiṁ me kuru te namaḥ

iti mantraṁ japantyas tāḥ | pūjāṁ cakruḥ kumārikāḥ

Translation:  Each of the Gopi performed her worship while chanting the following mantra. "O goddess Kātyāyanī, O great potency of the Lord, O possessor of great mystic power and mighty controller of all, please make the son of Nanda Mahārāja my husband. I offer my obeisances unto you."

The complete Katyayani vrat katha (Gauri Vrat Katha ) , Katyayani vrat vidhi (Gauri Vrat vidhi ) has also been Mentioned in Brahma vaivartha puran in Krishna Janma Khanda Chapter 27.
Lord Narayan himself narrates the story behind this to Lord Narada and mentions that this vrat is called Gauri vrat.So Gauri vrat and Katyayani vrat are one and the same and is observed in order to please Goddess Katyayani i.e. Goddess Durga.

This vrat was also observed by Devi Sita who was blessed by Devi Durga and was able to marry Prabhu Shri Ram.