Sri Nityananda Trayodashi is the auspicious appearance day of Sri Nityananda Prabhu. In the Caitanya Caritamrita and other scriptures, He is declared to be the avatar of Lord Balarama, the direct expansion of the Supreme Personality of Godhead, Krishna.
The Supreme Lord Sri Krishna appeared in Navadvipa, West Bengal as Sri Chaitanya Mahaprabhu to establish Sankirtana Movement (Congregational chanting of the holy name of the Lord, the Yuga-dharma for this age). To help the Supreme Lord in His mission, Lord Balarama appeared as Nityananda Prabhu. He assisted Sri Chaitanya Mahaprabhu by spreading the holy name of the Lord throughout Bengal.
Nityananda Prabhu appeared in the village of Ekachakra, in the district of Birbhum (West Bengal) as the son of Padmavati and Hadai Pandita in the year 1474 AD. He was born on the thirteenth day of the bright fortnight in the month of Magha (Magha Shukla Trayodashi). Even today pilgrims visit the place of birth of Lord Nityananda in Ekachakra. This temple is called Garbhavasa.
Nityananda Prabhu is also known as Premananda Sukhi, blissful as he always relishes the joy of love of Krishna Prema. On taking shelter of Lord Nityananda, he gives pure bliss to unhappy and conditioned souls who also can relish the pure love that comes from our bhakti.