Ariyalur district is a district of Tamil Nadu state with its administrative headquarters located at Ariyalur town. The district got its name from its headquarters town, Ariyalur. Legends believed that earlier the place, Ariyalur was popularly known as Hari Nindra or meaning the place where Hindu god Hari (Vishnu) stood. The Alanthurayar Kothandaramasamy Temple, situated at Ariyalur is the place from where the nine avatars of Hari carved out of a single stone. During different periods of time the place was ruled by different rulers from different dynasties such as dynasties of Pallavas, Cholas, Pandyas, Hoysalas, Vijayanagar, Palayam, Bijapur Sultans, Marathas, Carnatic Nawabs and finally British. The history of the district is also associated with a power struggle between Hyder Ali and later Tipu Sultan against the British. The British took the civil and military Administration of the Carnatic after the death of Tipu Sultan in 1801. So, Tiruchirappalli went into the hands of the British. After India got its independence, in 1995 Tiruchirappalli was bifurcated into the districts of Perambalur and Karur. Ariyalur was carved out of the Perambalur district and emerged as a separate district on 1st January, 2001. But, on 31st March, 2002 it was again merged with the Perambalur district. At last, Ariyalur was re-carved and came into existence as a separate district on 23rd November, 2007.

Geographically, the district lies at 11014'N latitude, 79008'E longitude and 75 m altitude. In the year 2019, there was a total 20.26% forest area of total geographical area. The district encompasses a geographical area of 1,940 sq. km. and it is bounded by Cuddalore district on the North, Thanjavur district on the South, Cuddalore district and Thanjavur district on the East and Perambalur district and Tiruchirapalli district on the West. Most of the rainfall in the district occurs in the monsoon season. The actual rainfall in the district was 1231.3 mm in the year of 2018-19.

Administration wise, the district is divided into 3 taluks namely Ariyalur, Udayarpalayam and Sendurai. Moreover, it comprises 3 sub-districts, 4 towns and 213 villages. The administrative language in the district is Tamil.

According to 2011 census the district has a population of 7,54,894 out of which 3,74,703 are males and 3,80,191 are females. The district has a sex ratio of 1015 (females for every 1000 males). During the year 2001-2011 the population growth rate in the district was 8.54% including 8.06% are males and 9.01% are females. As per 2011 census the major religion in the district is Hindu with 93.84% of the total population. The population density in the district is 389 persons per sq. km. According to 2011 census the principal language in the district is Tamil with 99.27%. In the year 2017 the number of live births in the district was 8,725 out of which 4,546 were males and 4,179 were females. In the same year the number of deaths in the district was 5,682 out of which 3,355 were males and 2,327 were females.

The economy of the district is mainly dependent on industrial sector. More than half of its population are directly or indirectly engaged in the industrial sector in order to earn their livelihood. Cement industry is the prime industry in the district and every year a huge chunk of revenue comes from the various cement industries in the district helps in its economy to a great extent. Some of the big cement units present in the district are Birlas (UltraTech Cement), India cements, Dalmia cements, Madras cements and many more. The Tamil Nadu government's undertaking TANCEM factory is the first cement producing factory in Ariyalur. In terms of agriculture, sugar cane and cashew are the foremost agricultural products in the district. The pre-dominate soil in the district is red sanding with scattered packers of black soil which is best suited for growing the dry crops. The district is also abundant in mineral resources. Some of the commonly found mineral resources in the district are lime stone, shale, sand stone, canker, phosphate nodules, etc. The gross domestic product in the district during the year 2011-12 was Rs. 2,52,802 lakhs at current price and Rs. 1,47,127 lakhs at constant prices in the year 2004-2005. The net domestic product in the district during the period 2012-13 was Rs. 4,57,683 lakhs at current price and Rs. 4,26,956 lakhs at constant prices in the year 2011-2012. The Per Capita Income or NDDP, At Factor Cost in the district during the period 2010-11 was Rs. 16,559 at constant prices in the year 2004-2005.

The district is well known as an abode of several reputed educational institutions. It provides a platform for higher education. As per 2011 census the literacy rate in the district is 71.34% including 81.23% are males and 61.74% are females. The total number of literates in the district is 4,80,604 including 2,69,582 are males and 2,11,022 are females.

The district has several centres of attraction which allures many travellers from different parts of the country as well as world. The Gandaikonda Cholapuram Siva temple, located in the district was constructed by Rajendra Chola I which comprises three stories and bounded by a huge fort like wall. There was also an outer wall but it was destructed almost completely during the period of British rule. Sri Kaliuga Varatharaja Perumaal temple, another significant temple is located 5 Km. away from the Ariyalur town. Rath Yatra meaning 'car festival' is the identity of this temple which is conducted every year during the month of March-April. Pilgrims from the far off places come to this temple during the period of Rath Yatra. Thirumazhapadi, a notable place is located on the bank of the Kollidam River in the district. Earlier, the place was ruled by the Chola dynasty thus, it is a historically significant place. Furthermore, one of the renowned temples in the district, Siva temple is situated in Thirumazhapadi. Karaivetti Bird Sanctuary, located at a distance of about 65 Km. from the Tiruchirappalli covers an area of over 454 hectares. More than fifty species of resident and migratory birds are found in this place during the month of November to February.