Nag Panchami, a.k.a., Naga or Nagula Panchami, is a Hindu festival dedicated to the worship of snakes and serpent deities. It is observed across India and Nepal on the fifth day of the bright fortnight of the lunar month of Shravan during the monsoon season. It celebrates the victory of Lord Krishna over the mythical Kaliya, a monstrous black python that was killed by Krishna in the Yamuna river. This year Nag Panchami falls on August 11, 2013.
Nine serpent deities are worshiped on the auspicious Nag Panchami day. Elaborate rituals in the form of 'puja' are held in temples and temporary altars in the honor of snake gods - Ananta, Vasuki, Padmanabha, Sesha, Kambala, Shankhapala, Dhruthrashtra, Takshaka and Kaliya - the nine prominent snake gods. In many parts of Eastern India Nag Panchami is dedicated to the serpent goddess, Manasa.
In Bengal and Bangladesh, the Manasa worship is a month-long affair spanning July and August. Devotees pay obeisance to goddess Manasa and perform various 'pujas' or rituals to appease her. Special 'murtis' or statues of the goddess are sculpted, various sacrifices made, and prayers chanted. In some places, worshippers are seen to pierce their bodies, poisonous snakes are displayed on the altar, and live shows depicting the life and legends of Manasa Devi are performed.