Chitwan National Park is the first national park of Nepal. It was established in 1973 as the Royal Chitwan National Park and was granted the status of a World Heritage Site in 1984. It covers an area of 952.63 km² (367.81 sq mi) in the Terai of south-central Nepal. It ranges in elevation from about 100 m (330 ft) in the river valleys to 815 m (2,674 ft) in the Sivalik Hills.

Since the end of the 19th century Chitwan used to be a favorite hunting ground for Nepal's ruling class during the cool winter seasons. Until the 1950s, the journey from Kathmandu to Nepal's south was arduous as the area could only be reached by foot and took several weeks. Comfortable camps were set up for the feudal big game hunters and their entourage, where they stayed for a couple of months shooting hundreds of tigers, rhinoceroses, elephant, leopards and sloth bears.

In 1950, Chitwan's forest and grasslands extended over more than 2,600 km² (1,000 sq mi) and were home to about 800 rhinos. When poor farmers from the mid-hills moved to the Chitwan Valley in search of arable land, the area was subsequently opened for settlement, and poaching of wildlife became rampant. In 1957, the country's first conservation law inured to the protection of rhinos and their habitat. Research of Chitwan was conducted by Edward Pritchard Gee during 1959 and 1963.

By the end of the 1960s, 70% of Chitwan's jungles had been cleared, malaria eradicated using DDT, thousands of people had settled there, and only 95 rhinos remained. The dramatic decline of the rhino population and the extent of poaching prompted the government to institute the Gaida Gasti – a rhino reconnaissance patrol of 130 armed men and a network of guard posts all over Chitwan. To prevent the extinction of rhinos, the Chitwan National Park was gazetted in December 1970, with borders delineated the following year and established in 1973, initially encompassing an area of 544 km² (210 sq mi).

When the first protected areas were established in Chitwan, Tharu people were forced to relocate from their traditional lands. They were denied any right to own land and thus forced into a situation of landlessness and poverty. When the national park was designated, Nepalese soldiers destroyed the villages located inside the boundary of the park, burning down houses and trampling fields using elephants. The Tharu people were forced to leave at gunpoint.

In 1977, the park was enlarged to its present area of 952.63 km² (367.81 sq mi). In 1997, a bufferzone of 766.1 km² (295.8 sq mi) was added to the north and west of the Narayani-Rapti river system, and between the south-eastern boundary of the park and the international border to India. The word 'Royal' was dropped from the park's name in 2006, at the end of the Nepalese Civil War.

Chitwan National Park has an area of 952.63 km² (367.81 sq mi) in the Terai region of southern Nepal at an elevation from about 100 m (330 ft) in the river valleys to 815 m (2,674 ft) in the Sivalik Hills; it encompasses parts of the Nawalpur, Chitwan, Makwanpur and Parsa Districts. The Narayani-Rapti river system forms a natural boundary to human settlements in the north and west. Adjacent to the east of Chitwan National Park is Parsa National Park, contiguous in the south is the Indian Tiger Reserve Valmiki National Park. The coherent protected area of 2,075 km² (801 sq mi) represents the Tiger Conservation Unit (TCU) Chitwan-Parsa-Valmiki, which covers a 3,549 km² (1,370 sq mi) huge block of alluvial grasslands and subtropical moist deciduous forests.

Chitwan has a humid subtropical monsoon influenced climate (Cwa) with high humidity all through the year. The area is located in the central climatic zone of the Himalayas, where monsoon starts in mid-June and eases off in late September. During these 14–15 weeks most of the 2,500 mm (98 in) annual precipitation falls. After mid-October, the monsoon clouds retreat, humidity drops off, and the top daily temperature gradually subsides from around 36 °C (97 °F) to 18 °C (64 °F). Nights cool down to 5 °C (41 °F) until late December, when it usually rains softly for a few days. Then temperatures start rising gradually.^{[citation needed]}