Annamalaiyar Temple is a Hindu temple dedicated to the deity Shiva, located at the base of Annamalai hills in the town of Thiruvannamalai in Tamil Nadu, India. It is significant to the Hindu sect of Saivism as one of the temples associated with the five elements, the Pancha Bhoota Stalas, and specifically the element of fire, or Agni. Shiva is worshiped as Annamalaiyar or Arunachaleswarar, and is represented by the lingam, with his idol referred to as Agni lingam. His consort Parvati is depicted as Unnamulai Amman. The presiding deity is revered in the 7th century Tamil Saiva canonical work, the Tevaram, written by Tamil saint poets known as the nayanars and classified as Paadal Petra Sthalam. The 9th century Saiva saint poet Manikkavasagar composed the Tiruvempaavai here.
The temple complex covers 10 hectares, and is one of the largest in India. It houses four gateway towers known as gopurams. The tallest is the eastern tower, with 11 stories and a height of 66 metres (217 ft), making it one of the tallest temple towers in India. The temple has numerous shrines, with those of Annamalaiyar and Unnamulai Amman being the most prominent. The temple complex houses many halls; the most notable is the thousand-pillared hall built during the Vijayanagar period.
The temple has six daily rituals at various times from 5:30 a.m. to 10 p.m., and twelve yearly festivals on its calendar. The Karthigai Deepam festival is celebrated during the day of the full moon between November and December, and a huge beacon is lit atop the hill. It can be seen from miles around, and symbolizes the Shiva lingam of fire joining the sky. The event is witnessed by three million pilgrims. On the day preceding each full moon, pilgrims circumnavigate the temple base and the Annamalai hills in a worship called Girivalam, a practice carried out by one million pilgrims yearly.
The present masonry structure was built during the Chola dynasty in the 9th century, while later expansions are attributed to Vijayanagar rulers of the Sangama Dynasty (1336–1485 CE), the Saluva Dynasty and the Tuluva Dynasty (1491–1570 CE). The temple is maintained and administered by the Hindu Religious and Charitable Endowments Department of the Government of Tamil Nadu.