S. Thomas' College, Mount Lavinia, is a fee-levying Anglican selective entry boys' private school in Sri Lanka. Started as a private school by James Chapman, the first Anglican Bishop of Colombo, in 1851, it was founded as a college and cathedral for the new Diocese of Colombo of the Church of Ceylon, modelled on British Public school tradition. An old boy of Eton College, Bishop Chapman founded the college on the Etonian model, the school's motto of Esto perpetua being derived from that of Eton College.

Dehiwala-Mount Lavinia, population 245,974 (2012), is a large municipality in Sri Lanka, covering 2,109 ha. It lies south of the Colombo Municipal Council area and is separated from it by the Dehiwala canal which forms the northern boundary of DMMC. Its southern limits lie in Borupana Road and the eastern boundary is Weras Ganga with its canal system and it includes some areas to its east. This town has experienced extensive population growth and rapid industrialisation and urbanisation in recent years. It is home to Sri Lanka's National Zoological Gardens, which remains one of Asia's largest. Colombo South Teaching Hospital, Kalubowila and Colombo Airport, Ratmalana are some important landmarks in this area. Dehiwela-Mount Lavinia and Sri Jayawardenapura Kotte being two large suburban centres of the city of Colombo function together as one large urban agglomeration in the Region. The overspill from the City in residential and commercial uses of land has rapidly urbanised these suburban centres. Dehiwela-Mount Lavinia and Sri Jayawardenpaura along with Colombo Municipal Council form the most urbanised part of the core area of the Colombo Metropolitan Region. Dehiwala and Mount Lavinia lie along the Galle Road artery, which runs along the coast to the south of the country.