The province was founded in 1579 (?) and was split into two, Camarines Norte and Sur in 1829. They were reunited under Ambos Camarines in 1854, but split again after three years. In 1893, they were reunited until March 10, 1917, when Philippine Republic Act 2711 formed most of the present-day provinces, including Camarines Norte and Camarines Sur.
In 1573, Miguel Lopez de Legaspi dispatched his grandson Juan de Salcedo to explore the region as far as Paracale in search of gold and other precious stones. A year later, Salcedo cruised the Bicol River and reached Bato Lake. Hence, the first recorded account of the discovery of the place.
In 1574, at the height of the Spanish colonization of the islands, Guido de Lavizares mentioned in his letter to the King of Spain the land of ""Los Camarines"" – apparently referring to the area of what is now Camalig, Albay, where rice storehouses and granaries or “camarin” abound. Thus, the name “Camarines” was coined and somehow stuck. Spanish colonizers later denominated the area into two distinct aggrupations.
Later, a Spanish garrison under Captain Pedro de Chavez was set up in Naga, a prosperous native rancheria. In 1575, de Guzman founded the Naga City, calling it Nueva Caceres after the birthplace of Governor General Francisco de Sande in Caceres, Spain.
On May 27, 1579, Governor General de Sande issued a decree which led to the establishment of a settlement in Camarines where Spanish colonists were urged to reside.
In 1636, Ibalon was split into two: Partido de Ibalon (comprising what is now Albay, Catanduanes, Sorsogon, Masbate, and the islands of Ticao and Burias) and Partido de Camarines (all towns north of present-day Camalig, Albay).
Partido de Camarines was further divided into Camarines Sur and Norte in 1829. From 1864 until 1893, Camarines Norte and Sur (collectively called Ambos Camarines) underwent a series of confusing geo-political division, fusion, re-division, and re-fusion, until in 1919 when the first Philippine Legislature finally separated Norte and Sur into two provinces. Its capital town then was Naga, the city once called ""Nueva Caceres"" – namesake of a province in Spain and among the original five royal cities of the colony.
The Philippine Revolution started in Ambos Camarines on September 17, 1898 when Elias Angeles and Felix Plazo, Filipino corporals in the Spanish Army, sided with revolutionists and fought the local Spanish forces. With the arrival of General Vicente Lukban, the revolutionary government in the Bicol region was established.
The American forces occupied the Bicol peninsula in January 1900. In March of the same year, General John M. Bell was made the military governor of Southern Luzon. Civil government was finally established in Ambos Camarines in April 1901.
In March 1919, the Philippine Legislature issued an Act authorizing the Governor General to divide the province into Camarines Norte and Camarines Sur.
During the outbreak of World War II, Wenceslao Q. Vinzons waged underground operations and organized guerilla units together with the Filipino and American troops against the Japanese troops stationed in Camarines Sur. After the capture of Vinzons on July 8, 1942, Lieutenant Francisco Boayes carried on with the guerilla movement. In April 1945, Camarines Sur was finally liberated from the Japanese invaders.