The Indian Himalayan Region (IHR) is spread between 21^o57' – 37 ^o 5'N latitudes and 72 ^o 40' – 97 ^o 25'E longitudes. It has an area of 5,31,250km² spread over 12 states and constitutes about 16.16% of India's total geographical area. This great chain of mountains in Indian territory extends all along the northern border of the country from the eastern border of Pakistan on the west to the frontiers of Myanmar in the east for about 2,500 km with an average width of 240 km. Orographically the Himalayan mountain system is divided into Greater Himalaya (Himadri) - area above the main central thrust consisting of snow-clad peaks, glaciers, and ranges of majestic mountains; Lesser Himalaya (Himanchal) - separated from the Himadri by the 'main central thrust' in the north and by the 'main boundary thrust' in the south, consisting of high mountains cut into deep ravines and precipitous defiles; and the Sub-Himalayan tract (Sivalik) - the foot-hill belt of the region - consisting of latest geological formation of loose boulders and soil.

Apart from the longitudinal divisions, the Indian Himalaya is also divided into following regional divisions based on population features and vegetation elements:
 
 

Western Himalaya	Central Himalaya	Eastern Himalaya
Kashmir Himalaya Himachal Himalaya	U.P. Himalaya	Arunachal Pradesh (including Sikkim & Darjeeling Hills) Purvanchal Himalaya

According to the regional characteristics, the Himalayan Kingdoms of Nepal and Bhutan fall under the central and eastern Himalaya, respectively.

Kashmir Himalaya: The Kashmir Himalaya occupies a geographical location between latitudes 32 ^o 17' - 37 ^o 5'N and longitudes 72 ^o 40' - 80 ^o 30'E, with a total area of 2,22,236km². The region lies at a strategic position in India with its borders touching Afghanistan in the north-west, Pakistan in the west, and China/Tibet in the north. Almost the whole of the Kashmir Himalaya is covered by a series of parallel mountain chains running in NW-SE direction. The region has three prominent thrusts viz., Murre, Panjal and Zaskar thrusts. The whole region can be differentiated into four broad groups viz., Karakoram, Ladakh, Zaskar and Pir Panjal, and these huge mountain ranges are separated by deep gorges forming the valleys of the Shyok, Indus, and Jhelum rivers, respectively.

Himachal Himalaya: The Himachal Himalaya lies between the latitudes 30 ^o 23' – 33 ^o 13'N and longitudes 75 ^o 43' – 79 ^o 4'E with a total area covering 55,673km². The state of Himachal Pradesh lies to the south of Kashmir. The state is bound in the east by Tibet (China), Garhwal region of Uttar Pradesh in the south-east, Punjab in the south-west, and in the south by Haryana. The region presents an intricate mosaic of mountain ranges, hills, and valleys and is known for its natural beauty. The Dhauladhar range in its supreme majesty overlooks the Kangra valley, while the Pir Panjal, the Great Himalaya and the Zaskar ranges stand guard over Chamba, Lahaul-Spiti, Kullu and Kinnaur respectively.

U.P. Himalaya: The Uttar Pradesh Himalaya popularly known as Uttarakhand is geographically located between latitudes 29 ^o 5' – 31 ^o 25'N and longitudes 77 ^o 45' – 81 ^o E covering an area of 51,124km². The Tons river separates the region from Himachal Pradesh in the north-west, while Kali separates it from Nepal in the east. Starting from the foot hills in the south the region extends upto the snow-clad peaks of the Himadri, marking the Indo-Tibetan boundary. The region being situated centrally in the long sweep of the Himalaya, forms a transitional zone between the per-humid eastern and the dry to sub-humid western Himalaya. The region comprises of two administrative units, Garhwal (north-west portion) and Kumaon (south-east portion).

Eastern Himalaya: The Eastern Himalayan region lies between the latitudes 26 ^o 40' - 29 ^o 30'N and longitudes 88 ^o 5' – 97 ^o 5'E and covers a total area of 93,988km² comprising Arunachal Pradesh, Sikkim and Darjeeling hills of West Bengal with 83,743, 7,096 and 3,149 km² of area respectively. In the north, the Himadri marks the international boundary with Tibet, which corresponds with the internationally accepted, well-known McMohan Line in the north-east. The Singalila range separates the region from Nepal in the west, while the Burma ranges of the Assam valley mark the eastern and southern boundary of the region. The Kingdom of Bhutan located between the Tibetan plateau and Assam-Bengal plains of India, separates Sikkim and Darjeeling hills from Arunachal Pradesh. The eastern boundary of the kingdom is Arunachal Pradesh while it is separated from Sikkim Himalaya by the Chumbi valley in the west.

Purvanchal Himalaya: It is the eastern extension of the concealed Peninsular Block of Shillong Plateau. This block merges in the Tertiary ranges of the Purvanchal Himalaya, which belongs to the great Arakan consisting of tightly packed parallel ridges and valleys. The Purvanchal Himalaya lies between the latitudes 21 ^o 5' - 28 ^o 23'N and longitudes 91 ^o 13' - 97 ^o 25'E, covering a total area of 108,229km² comprising Assam Hills (15,322km²), Manipur (22,327 km²), Meghalaya (22,429km²), Mizoram (21, 081km²), Nagaland (16,579km²), and Tripura (10,491km²). The region is extended in NE-SW direction touching the Tirap district of Arunachal Pradesh in the north-east and Chitagong Hill Tracts of Bangladesh in the south-west while the Assam valley is the northern boundary. The region lies at a strategic position in North-East India having international boundary both in the east and the west with Myanmar and Bangladesh respectively.