The South Luzon Expressway (SLEX),[c] signed as E2 of the Philippine expressway network and R-3 of the Metro Manila arterial road network, is a controlled-access highway that connects Metro Manila to the provinces in the Calabarzon, Mimaropa and Bicol Region on the island of Luzon in the Philippines.

The expressway also serves as a major utility corridor, carrying various high voltage overhead power lines and an oil pipeline.

The expressway consists of two sections: the 13.43-kilometer (8.35 mi) Skyway At-Grade segment, which runs underneath the Skyway from Magallanes Interchange in Makati to Alabang Exit in Muntinlupa,[7] and the 36.13-kilometer (22.45 mi) South Luzon Tollway (SLT) segment, also called the Alabang–Calamba–Santo Tomas Expressway (ACTEX), from Alabang to Santo Tomas, Batangas.

SLT/ACTEX is further divided into three phases:[4][9][10][11][12] The South Luzon Expressway starts as the physical extension of Osmeña Highway past the Magallanes Interchange, where it also meets Circumferential Road 4, particularly EDSA.

The expressway runs through 49.56 km (30.80 miles), spanning the cities of Makati, Pasay, Taguig, Parañaque, and Muntinlupa in Metro Manila and the provinces of Cavite, Laguna, and Batangas.

[5][14][15] Located then in the province of Rizal, the original stretch of the expressway, spanning approximately 15 kilometers (9.3 mi) from EDSA (Highway 54) in Magallanes, Makati to Alabang Exit in Muntinlupa, was constructed beginning in 1967 and was completed on December 16, 1969.

[3][17] In 1996, PNCC entered into a joint venture with Hong Kong-based Hopewell Holdings to modernize and extend the expressway.

[29] On February 1, 2006, a new agreement was signed between Malaysia-based MTD Berhad and PNCC to rehabilitate, extend, and operate the expressway.

The widening of the Alabang Viaduct from three to four lanes per direction, a phase known as the SLEX Toll Road 1, was completed on November 11, 2008.

[31] Toll Road 3, also known as the SLEX-STAR Tollway link, was then inaugurated on June 15, 2010, by President Gloria Macapagal Arroyo and opened to the public six months later on December 15, 2010, during the administration of her successor Benigno Aquino III, with the name Alabang–Calamba–Santo Tomas Expressway (ACTEX).

[34][35][36] In December 2022, the implementation of the Seamless Southern Tollways project began on SLEX to simplify the toll collection process to a single payment upon exit.

[37] In 2023, an expansion project began to widen the expressway's segment south of the SLEX Elevated Extension ramps to six (2x6) lanes per direction, necessitating the felling of 8,766 trees along the route.

[38][39] The project also involves the expansion of 20 bridges along SLEX and the demolition of the Calamba and Ayala Greenfield Estates toll plazas,[40] with completion targeted for December 2024.

[42] In addition, the Ayala Greenfield Interchange in Calamba broke ground on October 14, 2024, and construction is expected to begin in December 2024.

[4][45] The extension project is implemented by the Toll Regulatory Board and will be operated by the SMC SLEX, Inc. (formerly South Luzon Tollway Corporation).

The extension would decongest the existing national road between Santo Tomas and Lucena, and provide a modern alternate route for travellers from Quezon to the Bicol Region.

[1] Right of way has been secured for the initial three segments from Calamba to Tiaong, with ongoing efforts to acquire land for the remaining stretch up to Lucena.

The expressway's starting point has been relocated near the Ayala Greenfield Golf Course after several alignment adjustments prompted by right-of-way challenges.

On June 29, 2020, the Toll Regulatory Board issued a resolution to declare this project a Toll Road upon the request of, and based on the proposal submitted by the joint venture (JV) of the Philippine National Construction Corporation (PNCC) and San Miguel Holdings Corporation (SMHC).

The toll rates by vehicle class are as follows: The South Luzon Expressway currently has nine service areas, with four on the northbound and five on the southbound.