Thiruvarur (Tamil: [t̪iɾuʋaːɾuːɾ]) also spelt as Tiruvarur is a municipality in the Indian state of Tamil Nadu. It is the administrative headquarters of Thiruvarur district and Thiruvarur taluk. The temple chariot of the Thyagaraja temple, weighing 360 tonnes (790,000 lb) and measuring 96 feet (29 m) tall is the largest temple chariot in India. Thiruvarur is the birthplace of Tyagaraja, Muthuswami Dikshitar and Syama Sastri, popularly known as the Trinity of Carnatic music of the 18th century CE. Thiruvarur Thiyagarajaa Swaamy temple is older than Tanjore big temple.

Thiruvarur was a part of Thanjavur district until 1991. The Odambokki river passes through the centre of the town. Thiruvarur covers an area of 10.47 km² (4.04 sq mi) and had a population of 58,301 as of 2011. Out of total population of Tiruvarur, 1,403,348 in the district, 257,795 are in urban area and 1,006,482 are in rural area. 65,220 households are in urban, 261,999 are in rural area. It is administered by a selection grade municipality. The town is a part of the Cauvery delta region and agriculture is the major occupation. Roadways are the major means of transportation with a total of 94.06 km (58.45 mi) of district roads including three national highways passing through the town. The town was one of the five traditional capitals of the Chola empire, with one of the emperors of the dynasty, Kulothunga Chola I, having it as his capital. The town is believed to be of significant antiquity and has been ruled, at different times, by the Medieval Cholas, Later Cholas, Later Pandyas, Vijayanagar Empire, Thanjavur Nayaks, Marathas and the British. The town is known for the Thyagaraja temple, and the largest annual chariot festival in Asia, held in the month of April.

The historic name of the town was Aaroor (Arur) and it finds mention in the seventh century saiva canonical work, Tevaram. It was also called Śrīnagara in Sanskrit.

The term Thiru is added to all temple cities that are mostly revered by the verses of Tevaram, which is the case of Arur becoming Thiruvarur. Another name of Thiruvarur is Kamalaalayasetra, meaning the "holy place that is an abode of lotuses"; the town is also referred so due to the presence of the Kamalaalayam tank and the temple deity, Kamalambigai. During the British Raj, the town was termed Tiruvalur, Tiruvaloor, and Thiruvalur. As per the district and municipality websites, the district has the spelling "Tiruvarur", while the town has it as "Thiruvarur".

As per folk legend, Thiruvarur is mentioned as the capital town of a legendary Chola king, Manu Needhi Cholan, who killed his own son to provide justice to a cow.

Thiruvarur was one of the five traditional capitals of the Chola empire and the history of town revolves around the Thyagarajaswamy temple. Thiruvarur is mentioned in the saiva canonical work, Tevaram by Thirugnana Sambanthar, Tirunavukkarasar and Sundarar, the foremost Saivite saints of seventh–eighth century CE and classified as Padal petra stalam. Tirunavukkarasar mentions several traditions of the temple like Marghazhi Aathirai Vizha, Panguni Uttirai Perunaal and Veedhivitakanin Veedhi Panni. The granite structure of the temple was first constructed by Aditya Chola I (871–907 CE) in the ninth century CE and revamped during the reign of Rajaraja Chola I (985–1014 CE). The temple was upgraded and rebuilt with stone by Rajendra Chola I (1012–44 CE). The temple has inscriptions from both the emperors, later Cholas and Pandyas. The temple is believed to be an inspiration for Rajaraja Chola to build the Brihadeeswarar Temple, a UNESCO World Heritage Site.

Inscriptions from the temple indicate Thiruvarur as the capital of Kulothunga Chola I (1070–1120 CE), during which the town emerged a centre of saivism. After the fall of Cholas during the reign of Rajendra Chola III in the 13th century CE, the town was caught under a power struggle between the Pandyas and Hoysalas. The royal patronage continued and the town flourished as a cultural centre during the rule of the Nayaks, Vijayanagar kings and Marathas. During the period of Marathas, the town became a temporary home to the Nataraja of Chidambaram temple. The town was briefly captured by French troops led by Lally (1702–66 CE) in 1759 CE. The Thyagarajar temple was ransacked in a failed attempt to discover hidden treasure. During the attempt, six members of the temple, suspected to be spies of the British, were killed in an encounter. The province and Tanjore were annexed by British after the failed attempt of the French to attack the King of Tanjore. After independence, Thiruvaur continued to be a part of the Thanjavur district and Nagapattinam district until 1991 and 1997 respectively. Thiruvarur was made the headquarters of Tiruvarur district when it was carved out of Nagapattinam district in 1997. In modern days, Thiruvarur regarded as the origin of Carnatic music because of the birth of great three musicians of Carnatic music (Tyagaraja, Muthuswami Dikshitar and Syama Sastri - The trinity of Carnatic Music).

Thiruvarur is located at 9°17′N 79°18′E / 9.28°N 79.3°E / 9.28; 79.3. The town is bounded by Sukumar river in the north, Valaiyar river in the south while the Odambokki river flows through the centre. The town has an average elevation of 3 metres (9.8 ft) from the sea level. The municipality covers an area of 10.47 km² (4.04 sq mi) Thiruvarur is situated at a distance of 300 km from Chennai, 24 km (15 mi) from Nagapattinam, 40 km (25 mi) from Karaikal, 40 km (25 mi) from Mayiladuthurai and 56 km (35 mi) from Thanjavur. The town along with the district receives an annual rainfall of 1,260 millimetres (50 in). The town experiences tropical climate during summer; from March to May. The proximity to sea results in high humidity throughout the year and peaks 70% from August to May. The town has a plain terrain of alluvial soil consisting of sand, silt and clay. Vennar and Vettar, the tributaries of river Cauvery are the major water bodies around the town. Surface water canals contribute 89% to irrigation, while the rest 11% is accounted by dug wells and tube wells. Paddy is the major crop while the others being black gram, green gram, ground nut and gingely.