Casiguran , officially the Municipality of Casiguran, is a municipality in the province of Sorsogon, Philippines. According to the 2024 census, it has a population of 36,464 people.
Established in the year 1600, Casiguran was the first missionary parish of Sorsogon. When the Spaniards first set foot in this part of Luzon in the 1570s, Casiguran was considered as their center of Kabikolan.
In 1583, the Franciscan missionaries took over the evangelization work started by the Augustinians.
The 1818 census showed 1,023 native families paying tribute and they were coexisting with 28 Spanish-Filipino families in the area.
There are two compelling thoughts for the origin of the town's name.
The first is from the name of Gugurang, the supreme deity of the indigenous peoples of Bicol (called Ibalon during the pre-colonial era).
A second is a folk legend, which narrates that the name is phonetically derived from the Bikol phrase kasi gurang<nowiki/>' (literally translated, "because old") as it is Sorsogon's ancient kingdom.
Casiguran is located at the coast of Sorsogon Bay, at the south of Luzon island, making it a suburb of neighboring Sorsogon City. It is from Sorsogon City and from Manila.
Casiguran is politically subdivided into 25 barangays. Each barangay consists of puroks and some have sitios.
The Casiguran Schools District Office governs all educational institutions within the municipality. It oversees the management and operations of all private and public, from primary to secondary schools.