Casiguran, officially the Municipality of Casiguran (Filipino: Bayan ng Casiguran; Ilocano: Ili ti Casiguran), is a municipality in the province of Aurora in the Central Luzon (Region III) of the Philippines. The population was 24,313 at the 2015 census. In the 2016 electoral roll, it had 15,067 registered voters.

The municipality is home to the Amro River Protected Landscape.

According to folk legend, the name Casiguran was obtained from the Hispano-Filipino term Kasiguruhan which means "safety" or "assurance", such as a fortress or sanctuary for sailing ships during stormy weather. Another legend says that if an unmarried stranger comes to the place, he unavoidably falls in love and marries and most of the time stays for good.

Casiguran was founded by Spanish missionaries on 13 June 1609. Prior to their arrival, early settlers were the Dumagats and Aetas, followed by migrants from other parts of the Philippines. These migrants spoke different languages such as Ilocano, Visayan languages, Bikol languages, Kapampangan, Gaddang, Itawis and Ibanag, and from these a Kasiguranin dialect evolved.

In 1942, invading Japanese forces landed in the town of Casiguran. In 1945, Allied troops as well as Philippine Commonwealth forces and recognized guerrilla units during the Battle of Casiguran at the end of World War II. When the Philippines regained sovereignty in 1946, Aurora was still part of Tayabas Province (now Quezon Province) and Casiguran was a lone northern town. Its political jurisdiction is bounded on the north by the province of Isabela, on the west by Quirino, and on the south west by Barangay Dinadiawan, which was then the boundary between Baler and Casiguran.

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