Klang Valley (Malay: Lembah Klang) is an area in Malaysia comprising Kuala Lumpur and its suburbs, and adjoining cities and towns in the state of Selangor. An alternative reference to this would be Kuala Lumpur Metropolitan Area or Greater Kuala Lumpur. It is geographically delineated by Titiwangsa Mountains to the north and east and the Strait of Malacca to the west. The conurbation is the heartland of Malaysia's industry and commerce. As of 2012, the Klang Valley is home to roughly 7.5 million people. Klang Valley is home to a large number of migrants from other states within Malaysia and foreign workers largely from Indonesia, India and Nepal.
The valley is named after the Klang River, the principal river that flows through it, which is closely linked to the early development of the area as a cluster of tin mining towns in the late 19th century. Development of the region took place largely in the East-West direction (between Gombak and Port Klang) but the urban areas surrounding Kuala Lumpur have since grown south towards the border with Negeri Sembilan and north towards Rawang.
There is no official designation of the boundaries that make up Klang Valley but it is often assumed to comprise the following areas and their corresponding local authorities:
- Selangor district of Petaling
- Selangor district of Klang
- Klang Municipal Council
Even though the Klang Valley officially consists of separate cities and suburbs, integration between these cities is very high, with a highly developed road network and an expanding rapid transit system. Many expressways criss-cross the metropolis making cars the most convenient way to get around . This however has led to the Klang Valley's notorious traffic jams that span whole kilometres of expressways and make driving during peak hours exhausting. Since the 1990s new rapid transit systems such as the RapidKL Light Rail Transit (LRT) and the KL Monorail have been developed. These systems are currently undergoing extensive expansion, with the 2 LRT lines being expanded into outlying suburbs and upgraded to fully-fledged Mass Rail Transit systems, and a whole new MRT line being built from the southeastern suburb of Kajang to the northwestern suburb of Kota Damansara.
See also 
- 1998 Klang Valley water crisis
- Greater Kuala Lumpur
- Kuala Lumpur
- List of metropolitan areas in Asia by population
- Public Transport in Klang Valley