Mahanavami is celebrated on Ashwin Shukla Paksha Navami, the ninth and the final day of Durga Navratri or Durga Puja. On Maha Navami Goddess Durga is worshipped as Mahisasuramardini which means the Annihilator of the Buffalo Demon. It is believed that on Maha Navami day goddess Durga killed the demon Mahishasura. On this day, the goddess Durga is worshipped in the form of Aparajita also, by offering her sugarcane stalks. Matangi Dasamahavidya too, is worshipped on Mahanavami as a part of Dasamahavidya pooja in Navratri. Mukteshwari is the Goddess to be worshipped on ninth day of Navratri as part of Saptamatrika and Ashtamatrika puja. Goddess Siddhidatri puja is performed on Mahanavami day, by the Navadurga Shakteya sampradaaya people.
The precise rule is that if Ashtami and Navami merge before Sanyakal on Ashtami Tithi then Ashtami Puja and Navami Puja including Sandhi Puja are done on the same day. Navami Homa is performed on Maha Navami and it is the significant ritual during Durga Puja.
In the northern part of India, Kanya Pujan is observed on this day. Their feet are washed, kumkumis applied on the forehead and given gifts and new clothes by the worshippers. While in Gujarat, Mahanavmi is celebrated with Garba and dandiya raas as other eight days of Navratri. In the east, Navami is of great significance in Bengal as it is the last day of Durga Puja. In the southern region of India, Suhasini Puja is performed. Married women, a symbol of Maha Shakti, are offered the Shodasopachara Puja. Followers of Dus Mahavidyas worship Matangi on this day and Maa Siddhidhatri is worshipped by Navdurga Sampradaya followers.