Agnitheertham is connected to Lord Rama and Goddess Sita after their return from Lanka. Lord Rama after rescuing Goddess Sita from demon Ravana had visited this place while on their way back to Ayodhya Kingdom.

According to the legend, after killing demon Ravana, who also a half brahmin and an ardent devotee of Lord Shiva, Lord Rama had prayed to Lord Shiva to recompense his sins of killing a brahmin. He had bathed in the waters of Agnitheertham. This is the reason why bathing in holy Agnitheertham is said to atone past...
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sins of the devotees, making it one of prominent places to visit in Rameshwaram.

There is one more legend associated to this theertham. According to this legend, after their return from Lanka, Lord Rama had expressed doubts regarding the chastity of Goddess Sita because of which Goddess went through Agnipariksha.

Upon hearing the doubts raised on her, Goddess Sita has asked Lord Lakshmana, who is the brother of Lord Rama, to lit a fire. She then entered the fire and sat to prove her purity. Inspite of sitting within the fire, she wasn’t hurt and Lord Agni appeared to prove the chastity of Goddess.However, later Lord Angi to wash away his sin of touching Goddess Sita when she sat in fire, took bath in the sea and offered prayers to Lord Shiva. This place is now called as Agnitheertham.

It is believed that devotees can atone their sins by taking a bath in the holy waters of Agnitheertham. According to some belief, childless couples, if bathe in its water and offer prayers to Lord Shiva, are blessed with children. Many devotees come here to pray for children. It is also visited by devotees to pray for the peace and moksha of their ancestors and to perform rituals after the demise of their loved ones.