Rapid KL, with its 204.1 km (126.8 mi) of metro railway and 5.6 km (3.5 mi) of BRT carriageway, is part of the Klang Valley Integrated Transit System, operating throughout Kuala Lumpur and Selangor's satellite cities in the Klang Valley area.

It was followed by a federal government restructuring of public transport systems in Kuala Lumpur in the early 2000s after the bankruptcy of STAR and PUTRA Light Rapid Transit operators, the precursors to the Ampang/Sri Petaling Lines and Kelana Jaya Line respectively, and the creation of the Rapid KL brand.

In line with this, the 1981 Master Plan Transportation Study Report specifically recommended the implementation of a light rapid transit (LRT) system with exclusive rights-of-way and a capacity of 20,000 passengers per hour per direction.

The LRT project was revived with the signing of an agreement for Phase 1 of the STAR-LRT (abbreviation for Sistem Transit Aliran Ringan Sdn Bhd) in December 1992.

The 1997 Asian financial crisis aggravated the situation, and by November 2001, the two companies owed a combined total of RM 5.7 billion.

In 2002, both companies and their respective LRT services were bought over by Prasarana Malaysia, and operations of the lines eventually were transferred to Rapid KL.

[9] The bus service in Kuala Lumpur was also facing problems with lower ridership due to an increase in private car usage and a lack of capital investments.

The operation hours will be extended for certain stations when special events such as the final of Piala Malaysia[26] and the New Year's Eve countdown.

[30] On 10 September 2021, Rapid KL reduced its waiting times for trains and buses to support the growing number of workers going back to their reopened workplaces.

[33] The Chan Sow Lin-Putra Heights route serves the southern part of Kuala Lumpur and the town of Puchong in Selangor.

The Chan Sow Lin-Ampang route primarily serves the suburbs of Ampang in Selangor and Cheras in Kuala Lumpur, both of which are located in the northeastern region of the Klang Valley.

The Kajang Line and Putrajaya Lines serves to connect the city with the fringes of the Klang Valley, such as Sungai Buloh, Putrajaya, Cyberjaya, and Kajang, while also providing rail connection to neighbouring towns and cities such as Petaling Jaya (Damansara), Seri Kembangan and Cheras.

[39] The BRT Sunway Line, the world's first all-electric bus rapid transit system, has an exclusive right-of-way and operates on an elevated guideway that is not shared with normal road traffic.

Except for the underground section between the Pasar Seni and Damai, the entirety of the Kelana Jaya Line is elevated or at-grade.

Elevated stations, in most parts, were constructed in four major styles with distinctive roof designs for specific portions of the line.

Stations with island platforms allow easy interchange between north-bound and south-bound trains without requiring one to walk down/up to the concourse level.