Tamil Nadu is one of the 28 states of India. Its capital and largest city is Chennai. Tamil Nadu lies in the southernmost part of the Indian Peninsula and is bordered by the union territory of Pondicherry, and the states of Kerala, Karnataka, and Andhra Pradesh. It is bound by the Eastern Ghats in the north, the Nilgiri, the Anamalai Hills, and Palakkad on the west, by the Bay of Bengal in the east, the Gulf of Mannar, the Palk Strait in the south east, and by the Indian Ocean in the south.

Tamil Nadu is the eleventh largest state in India by area and the seventh most populous state. It is the fourth largest contributor (as of 2010) to India's GDP and ranks tenth in Human Development Index as of 2006. Tamil Nadu is also the most urbanised state in India. The state has the highest number (10.56%) of business enterprises and stands second in total employment (9.97%) in India, compared to the population share of about 6%.

The region has been the home of the Tamil people since atleast 500 BCE. Its official language Tamil has been in use in inscriptions and literature for over 2000 years. Tamil Nadu is home to many natural resources, Hindu temples of Dravidian architecture, hill stations, beach resorts, multi-religious pilgrimage sites and eight UNESCO World Heritage Sites.

History
Tamil Nadu's history dates back to pre-historic times. Archaeological evidence points to this area being one of the longest continuous habitations in India. In Adichanallur, 24 km (15 mi) from Tirunelveli, archaeologists from the Archaeological Survey of India unearthed 169 clay urns containing human skulls, skeletons and bones, plus husks and grains of rice, charred rice and Neolithic celts, giving evidence confirming them to be of the Neolithic period, 3800 years ago. The ASI archaeologists have proposed that the script used at that site is "very rudimentary" Tamil Brahmi. Adichanallur has been announced as an archaeological site for further excavation and studies. About 60% of the total epigraphical inscriptions found by ASI in India are from Tamil Nadu and most of which are in Tamil language. Geologists have discovered hundreds of fossilized dinosaur eggs, perhaps 65 million years old, underneath a stream in a tiny village in Ariyalur district. Researchers from the Salem-based Periyar University believe that the clusters of eggs belonged to the aggressive Carnosaur and the leaf-eating Sauropoda.

The Cholas who were very active during the Sangam age were entirely absent during the first few centuries. The period started with the rivalry between the Pandyas and the Pallavas, which in turn caused the revival of the Cholas. The Cholas went on to becoming a great power. Their decline saw the brief resurgence of the Pandyas. This period was also that of the re-invigorated Hinduism during which temple building and religious literature were at their best. The Cheras ruled in southern India from before the Sangam era (300 BCE – 250 CE) over the Coimbatore, Karur, Salem Districts in present day Tamil Nadu and present day Kerala from the capital of Vanchi Muthur in the west, (thought to be modern Karur). They traded extensively from nearby Muziris, in spices, ivory, timber, pearls and gems, with the ancient kingdoms of Egypt, Rome, Greece, Ceylon, Phoenicia, Arabia, Mesopotamia and Persia. The Kalabhras, invaded and displaced the three Tamil kingdoms and ruled between the third and the seventh centuries CE of the Sangam period. This is referred to as the Dark Age in Tamil history. They were expelled by the Pallavas and the Pandyas in sixth century.

Geography
Tamil Nadu covers an area of 130,058 square kilometres (50,216 sq mi), and is the eleventh largest state in India. The bordering states are Kerala to the west, Karnataka to the northwest and Andhra Pradesh to the north. To the east is the Bay of Bengal and the union territory of Pondicherry. The southernmost tip of the Indian Peninsula is located in Tamil Nadu. At this point is the town of Kanyakumari which is the meeting point of the Arabian Sea, the Bay of Bengal, and the Indian Ocean.

The western, southern and the north-western parts are hilly and rich in vegetation. The Western Ghats and the Eastern Ghats and they both meet at the Nilgiri hills. The Western Ghats dominate the entire western border with Kerala, effectively blocking much of the rain bearing clouds of the South West Monsoon from entering the state. The eastern parts are fertile coastal plains and the northern parts are a mix of hills and plains. The central and the south central regions are arid plains and receive less rainfall than the other regions.

Tamil Nadu has a coastline of about 910 kilometres (600 mi) which is the country’s third longest coastline. Tamil Nadu's coastline bore the brunt of the 2004 Indian Ocean Tsunami when it hit India, which caused 7,793 direct deaths in the state. Tamil Nadu falls mostly in a region of low seismic hazard with the exception of the western border areas that lie in a low to moderate hazard zone; as per the 2002 Bureau of Indian Standards (BIS) map, Tamil Nadu falls in Zones II & III. Historically, parts of this region have experienced seismic activity in the M5.0 range.

Climate
Tamil Nadu is heavily dependent on monsoon rains, and thereby is prone to droughts when the monsoons fail. The climate of the state ranges from dry sub-humid to semi- arid. The state has three distinct periods of rainfall:

The normal annual rainfall of the state is about 945 mm (37.2 in) of which 48% is through the North East monsoon, and 32% through the South West monsoon. Since the state is entirely dependent on rains for recharging its water resources, monsoon failures lead to acute water scarcity and severe drought. Tamil Nadu is classified into seven agro-climatic zones: north-east, north-west, west, southern, high rainfall, high altitude hilly, and Cauvery Delta (the most fertile agricultural zone). The table below shows the maximum and minimum temperatures that the state experiences in the plains and hills.