Sapta-sāgara Tīrtha means the tīrtha of the Seven Oceans. It is one of the sacred tīrthas named in the Āraṇya Kāṇḍa of the Vālmīki Rāmāyaṇa, in the region of Mataṅga hill and the southern parts of the forest of Daṇḍakāraṇya.

Where it is named

The Āraṇya Kāṇḍa names this tīrtha in connection with Śabarī’s long stay in the Mataṅga-vana (the forest of Mataṅga). It appears among the sacred places of the southern forest chapters, which describe the places visited or spoken of during Rāma’s journey to the south.

Sources

Vālmīki Rāmāyaṇa, Āraṇya Kāṇḍa, the southern forest chapters