Yarlung Tsangpo River in the context of "Arunachal Pradesh"

The Himalayas, or Himalaya, is a mountain range in Asia separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than 100 peaks exceeding elevations of 7,200 m (23,600 ft) above sea level lie in the Himalayas.

The Himalayas abut on or cross territories of six countries: Nepal, India, China, Bhutan, Pakistan and Afghanistan. The sovereignty of the range in the Kashmir region is disputed among India, Pakistan, and China. The Himalayan range is bordered on the northwest by the Karakoram and Hindu Kush ranges, on the north by the Tibetan Plateau, and on the south by the Indo-Gangetic Plain. Some of the world's major rivers, the Indus, the Ganges, and the Tsangpo–Brahmaputra, rise in the vicinity of the Himalayas, and their combined drainage basin is home to some 600 million people; 53 million people live in the Himalayas. The Himalayas have profoundly shaped the cultures of South Asia and Tibet. Many Himalayan peaks are sacred in Hinduism and Buddhism. The summits of several—Kangchenjunga (from the Indian side), Gangkhar Puensum, Machapuchare, Nanda Devi, and Kailash in the Tibetan Transhimalaya—are off-limits to climbers.

The Brahmaputra is a trans-boundary river which flows through Southwestern China, Northeastern India, and Bangladesh. It is known as the Brahmaputra or Luit in Assamese, Yarlung Tsangpo in Tibetan, the Siang/Dihang River in Arunachali, and Jamuna River in East Bengal. By itself, it is the 9th largest river in the world by discharge, and the 15th longest.

It originates in the Manasarovar Lake region, near Mount Kailash, on the northern side of the Himalayas in Burang County of Tibet where it is known as the Yarlung Tsangpo River. The Brahmaputra flows along southern Tibet to break through the Himalayas in great gorges (including the Yarlung Tsangpo Grand Canyon) and into Arunachal Pradesh. It enters India near the village of Gelling in Arunachal Pradesh and flows southwest through the Assam Valley as the Brahmaputra and south through Bangladesh as the Jamuna (not to be confused with the Yamuna of India). In the vast Ganges Delta, it merges with the Ganges, popularly known as the Padma in Bangladesh, and becomes the Meghna and ultimately empties into the Bay of Bengal.

The Transhimalaya (also spelled Trans-Himalaya), or Gangdise – Nyenchen Tanglha range (Chinese: 冈底斯-念青唐古拉山脉; pinyin: Gāngdǐsī-Niànqīngtánggǔlā Shānmài), is a 1,600-kilometre-long (990 mi) mountain range in China, India and Nepal, extending in a west–east direction parallel to the main Himalayan range. Located north of Yarlung Tsangpo river on the southern edge of the Tibetan Plateau, the Transhimalaya is composed of the Gangdise range to the west and the Nyenchen Tanglha range to the east.

The name Transhimalaya was introduced by the Swedish geographer Sven Hedin in the early 20th century. The Transhimalaya was described by the Columbia Lippincott Gazetteer in 1952 as an "ill-defined mountain area" with "no marked crest line or central alignment and no division by rivers." On more-modern maps the Kailas Range (Gangdise or Kang-to-sé Shan) in the west is shown as distinct from the Nyenchen Tanglha range in the east.

In geomorphology, drainage systems, also known as river systems, are the patterns formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land. Geomorphologists and hydrologists often view streams as part of drainage basins (and sub-basins). This is the topographic region from which a stream receives runoff, throughflow, and its saturated equivalent, groundwater flow. The number, size, and shape of the drainage basins varies and the larger and more detailed the topographic map, the more information is available.