Moisture-laden southeast trade winds, which dominate the weather from April to October, bring abundant annual rainfall (160–315 inches 【4,000–8,000 mm】) to the south and east of the island; the north and west sides, however, have as little as 25 inches (635 mm) of rain a year. Temperatures tend to be cool for the tropics, especially at higher elevations, but in summer the lowlands are uncomfortably humid. Tropical cyclones occur frequently.

Réunion was first settled in the 17th century by colonists from France. Slave labourers were brought in from East Africa to work on plantations, and later Malays, Annamites, Chinese, and Malabar Indians were imported as indentured labourers. Today most of the population is of mixed descent (Creole), with African descent predominant. The limited amount of land has induced substantial emigration, largely to France but also to Madagascar. The island's population density is high, even in areas that typically would be considered too mountainous to support a dense population. Saint-Denis, the capital and largest urban area on the island, contains almost one-fifth of the total population. The language in common use on the island is Creole (creole languages); French (French language), however, is the official language. About 90 percent of the population is Roman Catholic.

Réunion's economy has been based almost entirely on sugar for more than a century. Cane is grown on most of the cultivable land, though vanilla bean and some fruits and vegetables, tobacco, and geraniums (for perfume) are also produced. About a dozen big estates with milling facilities produce the bulk of the cane crop. Sugar represents about 75 percent of Réunion's exports, and such sugar by-products as rum and molasses account for much of the rest. Much of Réunion's trade is with France. Unemployment continues to be a problem. A few paved roads connect the main towns on the island. Le Port can handle large ships through artificial port facilities. An international airport is located near Saint-Denis.

As an overseas département of France, Réunion elects five deputies to the French National Assembly and three to the Senate. The département is administered by an appointed prefect and a general council composed of 44 elected members. There is also a regional council (created 1974) for Réunion that coordinates social and economic development policies. The Réunionese are full citizens of France, and classes in the département's schools are conducted in French.

Uninhabited when first visited by Portuguese navigators in the early 1500s, Réunion was settled in the mid-1600s, when the French East India Company established a layover station for ships rounding the Cape of Good Hope en route to India. African slaves were imported to work in first coffee and then sugar plantations; with the abolition of slavery in 1848, indentured labourers from Indochina, India, and East Africa were brought in. Réunion was ruled by France as a colony until 1946, when it became an overseas département of France; in 1974 it gained the status of région as well. The headquarters of the French military forces in the Indian Ocean were established on Réunion in 1973, with the arrival of personnel withdrawn from Madagascar. In the late 1970s the Organization of African Unity (now the African Union) urged that Réunion be granted full independence, but this proposition was not embraced by the majority of Réunion's inhabitants and thus was not pursued with any zeal.

Persistent social and economic unrest, fueled by the widening gap between the rich and the poor and by high rates of unemployment, periodically erupted into demonstrations and violence during the 1990s and 2000s. Rioting in February 1991 left 11 people dead, and in 1997 demonstrations were held against proposed civil service reforms. In 2000 a proposal made by the French government to split the island into two départements spawned demonstrations both for and against the division; the proposal was later rejected by the French Senate.