The Arunachalesvara Temple or Annamalaiyar Temple (Tamil: அண்ணாமலையார் திருக்கோவில்), is a historic Hindu temple dedicated to Shiva and Parvati, located at the foothills of the Annamalai hill in Tiruvannamalai, Tamil Nadu, India. It is regarded as one of the most significant temples in the Tamil Shaivite tradition and is associated with the element of fire (Agni) among the five classical elements (Pancha Bhoota Sthalams).

The presiding deity of the temple is Annamalaiyar (Tamil: அண்ணாமலையார்), a manifestation of Shiva, who is worshipped as the embodiment of the Arunachala (Annamalai) hill itself. His consort is known as Unnamulai Ammai (Tamil: உண்ணாமுலை அம்மை), a form of Parvati.

The temple holds immense religious and cultural significance in Tamil Shaivism and is celebrated in canonical Tamil devotional works such as the Thevaram, Thiruvempavai, and Thiruppugazh. It is classified as one of the Paadal Petra Sthalams, the sacred sites glorified in early medieval Tamil Saiva literature.

Shiva is worshipped as Annamalaiyar (meaning “The mountain that cannot be reached”), and is represented by the lingam known as the Agni Lingam, symbolizing the element of fire. Parvathi, revered as Unnamulai ammai (As per Thevaram Hymns), is represented by the yoni, with her idol referred to as the Agni Yoni.