The Chincha Islands War, also known as Spanish–South American War, was a series of coastal and naval battles between Spain and its former colonies of Peru, Chile, Ecuador, and Bolivia from 1865 to 1879. The conflict began with Spain's seizure of the guano-rich Chincha Islands in one of a series of attempts by Spain, under Isabella II, to reassert its influence over its former South American colonies. The war saw the use of ironclads, including the Spanish ship Numancia, the first ironclad to circumnavigate the world.

Isabella II was Queen of Spain from 1833 until her deposition in 1868. She is the only queen regnant in the history of unified Spain.