Arulmigu Veerateeswarar Temple, also known as Thirukoilur Veerattam, is located in Tirukoilur, a panchayat town in Kallakurichi district, Tamil Nadu. Dedicated to the Hindu god Shiva, the temple was constructed in the Dravidian architectural style during the Chola period in the 10th century. Shiva is worshipped as Veerateeswarar and his consort Parvathi as Periyanayagi. The temple is revered in the 7th-century Tamil Saiva canonical work, the Tevaram, and is classified as a Paadal Petra Sthalam.
The temple complex features two three-tiered Rajagopurams, or gateway towers, one each for Veerateeswarar and Periyanayagi. Enclosed by granite walls, the temple houses various shrines dedicated to Vinayakar, Murugan, Durga, and other deities. Rituals are performed six times daily, and the temple is open from 6 am to 12 pm and from 4 pm to 8:30 pm, except on new moon days when it remains open all day. Major festivals include Masimaham, Karthigai Somavaram, and the Manickavasagar festival.
As per Hindu legend, Shiva appeared as Andakasura samhara murthy to slay the demon king Andakasura, who lusted after Parvathi. After being defeated, Andakasura was reborn as Shiva’s devotee, Gana Bhringi. The temple's importance is also referenced in Sangam literature from the 3rd century BCE to the 3rd century CE. The poet Kapilar’s self-immolation and Avvaiyar’s contributions to this sacred site are commemorated during the Maasi Magam festival.
Architecturally, the temple is noted for its large granite rectangular structures and sanctum sanctorum, which houses the Lingam form of Shiva. The sanctum is approached through pillared halls, including the Ardha Mandapa and Mukha Mandapa. The second precinct contains the shrine of Periyanayagi and is similarly structured. Contributions by the medieval chieftain Rajanarayana Sambuvaraya helped revive temple services, as documented in various inscriptions across Tamil Nadu.