Krishnagiri district is a district of the Tamil Nadu state with its administrative headquarters located at Krishnagiri town. The district got its name from its headquarters town. The name of the place, Krishnagiri is derived from the two words one is 'Krishna' refers to the colour 'black' and another one is 'giri' means 'hill' since the place has numerous granite hillocks. Some legends believe that probably the place was named after Krishna Deva Raya, a ruler who ruled the place long ago. On the basis of the evidences found by the Archeological research, it has been proved that during the Paleolithic, Neolithic and Mesolithic ages there was the presence of habitats of mankind in the place. Earlier, the Krishnagiri region was a part of the ancient Kongu Nadu and Chera country. The Kongu and Chera rulers ruled the place for a long time. Later, the region was ruled by different rulers during the different periods of time likewise, Cholas, Pallavas, Gangas, Nulambas, Hoysalas, Vijaya Nagar and Bijapur emperors, Wodeyars of Mysore and Nayaks of Madurai. During Mysore war I the British troops passed through the place, Krishnagiri to attack Hyder Ali's Forces at 'Kaveripattinam'. On the other hand British force was defeated in this place. In Mysore war II the entire region of Salem and Karnataka came under Hyder Ali's control. Hyder Ali fought bravely against the English at Krishnagiri. This region of Krishnagiri is popularly known as "Gateway of Tamil Nadu" since it stands as a protective barrier for the Tamil Nadu. Previously, the present Krishnagiri district was a part of the Dharmapuri district but it was emerged as a separate district on 2nd September, 2004.

Geographically, the district lies at 12°52'N latitude, 78°21'E longitude and 632 m altitude. In the year 2021, there was a total 31.55% forest area of total geographical area. The district encompasses a geographical area of 5,129 sq. km. and it is bounded by Andhra Pradesh on the North, Dharmapuri district on the South, Vellore district and Thiruvannamalai district on the East and Karnataka on the West. Generally, the climate of its eastern part remains hot whereas its western part enjoys a pleasant climate. Most of its rainfall occurs in the monsoon season. The actual rainfall in the district was 944.1 mm in the year of 2021-22.

Administration wise, the district is divided 5 taluks namely Krishnagiri, Hosur, Pochampalli, Uthangarai and Denkanikottai. Moreover, it comprises 5 sub-districts, 14 towns and 655 villages. The administrative language in the district is Tamil.

According to 2011 census the district has a population of 18,79,809 out of which 9,60,232 are males and 9,19,577 are females. The district has a sex ratio of 958 (females for every 1000 males). During the year 2001-2011 the population growth rate in the district was 20.41% including 19.57% were males and 21.31% were females. As per 2011 census the major religion in the district is Hindu with 91.70% of the total population. The population density in the district is 367 (persons per sq. km.). According to 2011 census the principal language in the district is Tamil with 58.23%. In the year 2020 the number of live births in the district was 25,181 out of which 12,918 were males and 12,263 were females. In the same year the number of deaths in the district was 14,391 out of which 8,784 were males and 5,607 were females.

The economy of the district is mainly dependent on both the sectors of agricultural and industrial. The chief agricultural products in the district are paddy, maize, ragi, banana, sugarcane, cotton, tamarind, coconut, mango, groundnut, etc. Mangoes of the Krishnagiri are famous throughout the country. Every year a huge chunk of revenue comes from these agricultural products in the district helps in its economy to a great extent. Fishery is a source of extra income for its natives. Mining and forestry based industries are the commonly found industries in the district. More than half of its population are directly or indirectly engaged in these industries in order earn their livelihood. In the year 2011-12 the gross domestic product in the district was Rs. 19,28,405 lakhs at current price and Rs. 12,38,339 lakhs at constant prices in the year 2004-2005. The net domestic product in the district during the period 2018-19 was Rs. 49,08,608 lakh at current price and Rs. 38,35,455 lakh at constant prices in the year 2011-2012. The Per Capita Income or NDDP, At Factor Cost during the period 2016-17 was Rs. 1,80,444 at current price and Rs. 1,48,147 at constant prices in the year 2011-2012.

The district is well known as an abode of several reputed educational institutions. It provides a platform for higher education. Sri Vidya Mandir Matriculation Higher Secondary School, located in Uthangarai is one of the topmost schools first in India. The main objective behind the establishment of the St. James Tailoring Institute in the district is to uplift the education of women in dress making technology. As per 2011 census the literacy rate in the district is 71.46% including 78.72% are males and 63.91% are females. The total number of literates in the district is 11,87,958 including 6,67,062 are males and 5,20,896 are females.

Chakravarti Rajagopalachari, the first and the last Indian Governor-General of India was born on 10th December, 1878 at Thorapalli in the district. He was a prominent leader of the Indian National Congress.

The district has several centres of attraction which allures many travellers from different parts of the country as well as world. The Krishnagiri Reservoir project, located near to the Krishnagiri town was created in the year 1958 during the rule of the then Chief Minister Kamaraj. Sayed Basha hills, in the district has a fort which was built by the ruler named Tippu Sultan, as his fortress. Rajaji Memorial is located at a distance of 10 km. from Hosur near Onnalvadi. The Tamil Nadu Government has converted the house of the great leader called Rajaji into a memorial and in his memory the memorial was named as Rajaji Memorial. Some other notable places of interest in the district are Rayakottah fort, Mallachandram, Government Museum, Kelevarapalli Reservoir Project and many more.