Riesi is a comune (municipality) in the Province of Caltanissetta in the Italian region Sicily, located about 110 kilometres (68 mi) southeast of Palermo and about 20 kilometres (12 mi) south of Caltanissetta. As of 31 December 2004, it had a population of 11,678 and an area of 66.6 square kilometres (25.7 sq mi).

Riesi was founded in the 13th century. In the period of Arab rule over the island, the area was called "abandoned place" or "fallow".

Until the 1920s, many of the city's inhabitants worked in the nearby sulphur mines Trabbia and Tallarita. The owners of the mine greatly exploited the impoverished population. Many families had to let their children work in the mines as indentured servants in order to survive. As you enter the city today, there is a large memorial commemorating the sufferings of the miners.

In 1961, the Waldensian minister Tullio Vinay founded the "Servizio Cristiano" (Christian service) to fight poverty. In the beginning, the key aims were to promote literacy among children and teenagers and later initiatives to promote agriculture and vocational training. Today, the Waldensian church operates a kindergarten, an elementary school, a guest house, a family health centre, and a small farm.