Casiguran, officially the Municipality of Casiguran, is a municipality in the province of Sorsogon, Philippines. According to the 2020 census, it has a population of 35,602 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.