Kathmandu (alter Name: Kantipur) liegt im Zentrum des dicht besiedelten Kathmandutales, einem in 1.300 m Höhe liegenden Talkessel von etwa 30 km Durchmesser. Die weiteren Städte im Tal, Lalitpur (Patan), Bhaktapur, Madhyapur-Thimi, Kirtipur und zahlreiche kleinere Gemeinden bilden einen Ballungsraum von über 1 Million Einwohnern (Zensus 2001: 915.071) Die umliegenden Berge haben Höhen zwischen 2000 und 2700 m. Im Norden, und mehr noch im Westen, haben die Ausläufer der Stadt den Fuß dieser Berge schon erreicht. Die Stadt erstreckt sich an der Nordseite des Bagmati. Der Kernbereich liegt zwischen den Flüssen Vishnumati und Dhobi Khola. An der Südseite des Bagmati liegt die Schwesterstadt Lalitpur (Patan).
Kathmandu is the capital and, with close to one million inhabitants, the largest metropolitan city of Nepal. The city is the urban core of the Kathmandu Valley in the Himalayas, which contains two sister cities: Lalitpur (Patan), 5 kilometres (3.1 mi) to its south and Bhaktapur or Bhadgaon, 12 kilometres (7.5 mi) to its east, and a number of smaller towns. It is also acronymed as 'KTM' and named 'tri-city'.[4] In the last census (2001), the city of Kathmandu had 671,846 inhabitants. Population estimates for 2005 were 790,612 and for 2010 they stood at 989,273 The municipal area is (50.67 square kilometres (19.56 sq mi))[5] and the population density is 19,500 per km².

The city stands at an elevation of approximately 1,400 metres (4,600 ft) in the bowl-shaped valley in central Nepal surrounded by four major hills, namely: Shivapuri, Phulchowki, Nagarjun and Chandragiri. Kathmandu valley is part of three districts, Kathmandu District, Lalitpur District and Bhaktapur District, with the highest population density in the country and accounting for about 1/5 of its population.

Kathmandu is not only the capital of the Federal Democratic Republic of Nepal but also the headquarters of the Central Region (Madhyamanchal) among the five development regions constituted by the 14 administrative zones of Nepal located at the central part of the country. The Central region has three zones namely, Bagmati, Narayani and Janakpur. Kathmandu is located in the Bagmati Zone.[6]

Kathmandu, as the gateway to Nepal Tourism, is the nerve centre of the country’s economy. With the most advanced infrastructure among urban areas in Nepal, Kathmandu's economy is tourism centric accounting for 3.8% of the GDP in 1995–96 (had declined since then due to political unrest but has picked up again).

The city’s rich history is nearly 2000 years old, as inferred from an inscription in the valley. Its religious affiliations are dominantly Hindu followed by Buddhism. People of other religious beliefs also live in Kathmandu giving it a cosmopolitan culture. Nepali is the common language of the city, though many speak the Nepal Bhasa as it is the center of the Newar (meaning: citizens of Nepal) people and culture. English is understood by the educated population of the city. Besides a significant number of the population speaks any of the foreign languages like : French, German, Chinese, Hebrew, Korean etc. The literacy rate is 99% in the city.[7]

From the point of view of tourism, economy and cultural heritage, the sister cities of Lalitpur (Patan) and Bhaktapur are integral to Kathmandu. The cultural heritage recognition under the World Heritage list of the UNESCO has recognized all the monuments in the three cities as one unit under the title “Kathmandu Valley-UNESCO World Heritage Site