The 222-kilometre-long (138 mi) highway links the Sri Lankan capital Colombo with Galle, Matara and Hambantota, major cities in the south of the island.

The Southern Expressway Project (SEP) was introduced by the Road Development Authority and the Ministry of Highways as far back as late 1980s.

The University of Moratuwa undertook an Environment Impact Assessment study in 1996, which was submitted to the government in early 1997.

The construction of the expressway was partly funded by the Japan Bank for International Cooperation, who were responsible for the 65 km (40 mi) section between Kurundugahahetekma and Kokmaduwa, and the Asian Development Bank, responsible for the 161 km (100 mi) section between Kurundugahahetekma and Pinnaduwa.

On 23 February 2020, The final stage of the expressway which links to Hambanthota was opened to the public.