The island of Sri Lanka lies in the Indian Ocean, to the southwest of the Bay of Bengal. It is separated from the Indian subcontinent by the Gulf of Mannar and the Palk Strait. According to Hindu mythology, a land bridge to the Indian mainland, known as Rama's Bridge, was constructed during the time of Rama by the vanara architect Nala. Often referred to as Adam's Bridge, it now amounts to only a chain of limestone shoals remaining above sea level. According to colonial British reports, this is a natural causeway which was formerly complete, but was breached by a violent storm in 1480. The island consists mostly of flat-to-rolling coastal plains, with mountains rising only in the south-central part. Amongst these is the highest point Pidurutalagala, reaching 2,524 metres (8,281 ft) above sea level. May, the hottest period, precedes the summer monsoon rains.

The rainfall pattern is influenced by monsoon winds from the Indian Ocean and Bay of Bengal: as the winds encounter the mountain slopes of the Central Highlands, they unload heavy rains on the slopes and the southwestern areas of the island. Between December and March, monsoon winds come from the northeast, bringing moisture from the Bay of Bengal. Humidity is typically higher in the southwest and mountainous areas and depends on the seasonal patterns of rainfall, and places like Colombo experience daytime humidity above 70% all year round, rising to almost 90% during the monsoon season in June. Anuradhapura experiences a daytime low of 60% during the monsoon month of March, but a high of 79% during the November and December rains. In the highlands, Kandy's daytime humidity usually ranges between 70% and 79%.

Sri Lanka is the 53rd most populated nation in the world, with an annual population growth rate of 0.79%. Sri Lanka has a birth rate of 15.63 births per 1,000 people and a death rate of 6.49 deaths per 1,000 people. Population density is highest in western Sri Lanka, especially in and around the capital. There is a small population on the island of the Vedda people. They are believed to be the original indigenous group to inhabit the island. The Sinhalese people form the largest ethnic group in the nation, composing approximately 81.9% of the total population.Tamils are concentrated in the North, East, Central and Western provinces of the country. Sri Lankan Tamils are the second major ethnic group on the island and have called it home for generations. Indian Tamils who were brought as indentured labourers from India by British colonists to work on estate plantations, nearly 50% of whom were repatriated following independence in 1948, are called "Indian Origin" Tamils. They are distinguished from the native Tamil population that has resided in Sri Lanka since ancient times

Buddhists are distributed across most parts of the island except in the north. Hindus are concentrated in north, east, and central high lands, though high populations also exists in the capital city of Colombo and in the surrounding suburbs. Christians, particularly Roman Catholics are mainly concentrated along the western coastal belt. Muslims are concentrated in several pockets along the coast and in theinterior. All religious communities are represented in the western province and in other urban centres in sizeable numbers. Sri Lanka was ranked the 3rd most religious country in the world by a 2008 Gallup poll, with 99% of Sri Lankans saying religion is an important part of their daily life.