The Klang Valley Integrated Transit System is an integrated transport network that primarily serves the area of Klang Valley and Greater Kuala Lumpur. The system commenced operations in August 1995 with the introduction of commuter rail service on the existing rail between Kuala Lumpur and Rawang. The system have since expanded and currently consists of 11 fully operating rail lines in a radial formation; two commuter rail lines, six rapid transit lines, one bus rapid transit line and two airport rail links to the Kuala Lumpur International Airport's (KLIA) Terminal 1 and Terminal 2, and one temperarily suspended airport rail link to the Sultan Abdul Aziz Shah Airport. The system encompasses 528.4 kilometres (328.3 mi) of grade-separated route on standard gauge and metre gauge with 197 operational stations.

Kuala Lumpur, officially the Federal Territory of Kuala Lumpur and colloquially referred to as KL, is a federal territory and the capital city of Malaysia. It is the largest city in the country, covering an area of 243 km2 (94 sq mi) with a census population of 2,163,000 as of 2022. Greater Kuala Lumpur, also known as the Klang Valley, is an urban agglomeration of 8.622 million people as of 2023. It is among the fastest growing metropolitan regions in Southeast Asia, both in population and economic development. Klang Valley is ASEAN's fifth largest economy after Singapore, Jakarta, Bangkok, and Manila.