The area where the city lies was identified as Cacicazgo de Jagua by early Spanish conquistadors. It was originally settled by Taino indigenous people. Cacicazgo translates from the Taino language as "chiefdom". Cacicazgo de Jagua was therefore the chiefdom of Chief Jagua.
The city was later settled by French immigrants from Bordeaux and Louisiana led by Don Louis de Clouet on April 22, 1819. The settlers named the city Fernandina de Jagua in honor of King Ferdinand VII of Spain and Chief Jagua. The settlement successively became a town (villa) in 1829, renamed for José Cienfuegos, Captain General of Cuba (1816–19), and a city in 1880. Many of the streets in old town reflect French origins in their names: Bouyón, D'Clouet, Hourruitiner, Gacel, and Griffo, for instance.
Cienfuegos port, despite being one of the latest settlements established during the colonial era, soon grew to be a powerful town due to the fertile fields surrounding it and its position on the trade route between Jamaica and South American cities to the southeast and the hinterland provincial capital of Santa Clara to the northeast. Its advantageous trading location on the historically eponymous Bay of Jagua was used by the Cuban sugar oligarchy when a railroad was built between both cities between 1853 and 1860.
Near Cienfuegos was the scene of a battle during the Spanish–American War on May 11, 1898, between American Marines attempting to sever underwater Spanish communication lines and the Spanish defenders.
During the Cuban Revolution, the city saw an uprising against Fulgencio Batista and was bombed in retaliation on September 5, 1957.
In 1969 and 1970, Soviet naval vessels visited the city. This appeared to be in violation of the Kennedy-Khrushchev agreements of 1962. However, there was no notice given by the United States and no confrontation ensued.
In 2005, Hurricane Dennis made its second landfall near Cienfuegos at about 1:00 AST (17:00 UTC) with winds of 232 km/h (144 mph) and gusts reaching 285 km/h (177 mph).
Near the entrance to Cienfuegos Bay is Castillo de Jagua (full name: Castillo de Nuestra Señora de los Angeles de Jagua), a fortress erected in 1745 for protection against Caribbean pirates.
Cienfuegos, one of the chief seaports of Cuba, is a center of the sugar trade as well as coffee and tobacco. While sugarcane is the chief crop, local farmers also grow coffee.
In 2004, the municipality of Cienfuegos had a population of 163,824. With a total area of 333 km2 (129 sq mi), it has a population density of 492.0/km2 (1,274/sq mi).
According to the Köppen Climate Classification system, Cienfuegos has a tropical savanna climate, abbreviated "Aw" on climate maps.
In 2005, UNESCO inscribed the Urban Historic Centre of Cienfuegos on the World Heritage List, citing Cienfuegos as the best extant example of early 19th century Spanish Enlightenment implementation in urban planning.
The downtown area contains six buildings from 1819–50, 327 buildings from 1851–1900, and 1188 buildings from the 20th century. There is no other place in the Caribbean which contains such a remarkable cluster of Neoclassical structures.
Cienfuegos fields a team in the Cuban National Series, the Cienfuegos Elefantes. Since joining the league in 1977–78, the best finish the Camaroneros have achieved is a 3rd place showing in the 2010–11 Cuban National Series. Despite finishing with the best record at 59–31, the Elefantes lost the semifinals in six games to the eventual champions, the Pinar del Río Vegueros.