The mountainous north contains eight of the world's ten highest mountains, including the highest, Mount Everest.

Nepal is commonly divided into three physiographic areas: the Mountain, Hill, Siwalik region and Terai Regions. These ecological belts run east-west and are vertically intersected by Nepal's major, north to south flowing river systems.

The southern lowland Plains bordering India are part of the northern rim of the Indo-Gangetic plains. They were formed and are fed by three major rivers: the Kosi, the Narayani, and the Karnali. This region has a hot, humid climate.

The Hill Region (Pahad) abuts the mountains and varies from 1,000 to 4,000 metres (3,300–13,125 ft) in altitude. Two low mountain ranges, the Mahabharat Lekh and Shiwalik Range (also called the Churia Range) dominate the region. The hilly belt includes the Kathmandu Valley, the country's most fertile and urbanised area. Unlike the valleys called Inner Tarai (Bhitri Tarai Uptyaka), elevations above 2,500 metres (8,200 ft) are sparsely populated.

The Mountain Region, situated in the Great Himalayan Range, makes up the northern part of Nepal. It contains the regions of highest altitude in the world; the world's highest mountain, 8,850 metres (29,035 ft) height Mount Everest (Sagarmatha in Nepali) is located here on the border with Tibet. Seven other of the world's ten highest mountains are located in Nepal: Lhotse, Makalu, Cho Oyu, Kanchenjunga, Dhaulagiri, Annapurna and Manaslu.

Nepal experiences five seasons: summer, monsoon, autumn, winter and spring. The Himalaya blocks cold winds from Central Asia in the winter and forms the northern limit of the monsoon wind patterns. In a land once thickly forested, deforestation is a major problem in all regions, with resulting erosion and degradation of ecosystems.