Matsya Avatara is the first Avatara of Lord Vishnu. Lord Vishnu’s fish incarnation also marks the beginning of Dashavatara. The story of Matsya Avatara is also mentioned in Padma Purana’s Uttara Khanda.
Once, goddess Parvati expressed her desire to know about all the incarnations of Lord Vishnu.
Lord Mahadeva replied– Lord Brahma had created numerous Prajapatis like Bhrigu, Marichi, Atri, Daksha, Kardam, Pulastya, Pulaha, Angira and Kratu. Marichi was the father of Kashyapa.
Sage Kashyapa had four wives–Aditi, Diti, Kadru and Vinta.
Aditi was the mother of Deities while Diti gave birth to demons like–Makar, Hayagreeva, Mahabali, Hiranyaksha, Hiranyakashipu Jambha, Maya etc. Makar was a mighty demon, who after deceitfully acquiring the Vedas from Lord Brahma had hidden himself inside an ocean.
Lord Brahma requested Vishnu to liberate the sacred Vedas from the possession of Makar.
Lord Vishnu then took the incarnation of Matsya and after killing Makar gave back the vedas to Lord Brahma. To kill demon Makar and recover Vedas from him, Lord Vishnu incarnated as Matsya Bhagawan and accomplished his duty.
There are very few temples dedicated to Matsya. Prominent ones include the Shankhodara temple in Bet Dwarka and Vedanarayana Temple in Nagalapuram. The Koneswaram Matsyakeswaram temple in Trincomalee is now destroyed. Matsya is generally enlisted as the first avatar of Vishnu, especially in Dashavatara (ten major avatars of Vishnu) lists. However, that was not always the case. Some lists do not list Matsya as first, only later texts start the trend of Matsya as the first avatar.
Matsya is the patron deity of the Meenas, who claim descent from the deity. The Meenas call Matsya Meenesh, the Lord of the Meenas or the fish (Meena) Lord. In Rajasthan there are many temples of Meenesh, but the first Meenesh temple was in Pushkar, Rajasthan. A Meenesh temple is also situated in Malarana chour village of Sawai Madhopur district of Rajasthan. Other temples include Meenangadi Matsyavathra Mahavishnu Temple and Matsya Narayana Temple, Bangalore.
The annual festival of Matsya Jayanti (Meenesh Jayanti in the Meena context), marking the birthday of Matsya, is celebrated on Chaitra Shukla Paksha Tritya, the third day of Chaitra Month (March- April).