South Sikkim is a district of the Indian state of Sikkim. Its capital is Namchi.

South Sikkim lies at an altitude of 400 to 2000 metres and hence enjoys a temperate climate for most of the year. Major urban centres include Namchi, Ravangla, Jorethang and Melli.

It is the most industrialised district in the state, owing to the availability of flat land. Since the geology is stable the roads are in a good condition as compared to other parts of the state which suffer from landslides. The district is also famous for its Sikkim Tea, which is grown near Namchi.

According to the 2011 census South Sikkim district has a population of 146,742, roughly equal to the nation of Saint Lucia.This gives it a ranking of 600th in India (out of a total of 640).The district has a population density of 196 inhabitants per square kilometre (510/sq mi).Its population growth rate over the decade 2001-2011 was 11.57%.South Sikkim has a sex ratio of 914 females for every 1000 males, and a literacy rate of 82.06%.

In 1987 in South Sikkim district the Maenam Wildlife Sanctuary was established, which has an area of 35 km2 (13.5 sq mi).