Thirunelli Temple is a major Hindu temple in northern Kerala Brahmagiri hills. The temple is notable for being a place where the devotees can perform all the rites-of-passage ceremonies ranging from those related to birth of children to the post-cremation dedication of cremation of ashes into natural water stream.

The temple is also known as 'Sahyamala Kshetram and Kashi of the South.

Thirunelli Temple is a pilgrimage site, particularly for South Indian Hindus to perform ancestral rites. The rituals are performed on the banks of the stream Papanasini which flows down from Mount Brahmagiri, ultimately joining Kerala rivers and meeting the oceans. The stream is called Papanasini (Sanskrit: Papa + nasini) because it is believed to have the power to dissolve sins.

The temple is very old and dedicated to Vishnu, designed according to Hindu texts for temple architecture in the midst of lush forests enclosed by mountains. It has a medieval era aquaduct that brought water from the mountains that surround it. On the west of this Maha Vishnu temple is a small cave temple Gunnika, dedicated to Shiva. The temple architecture and iconography celebrates Brahma, Vishnu and Shiva, as well as goddesses of Hinduism.