Cagayancillo is a municipality in Palawan Province, a group of 31 islands in the middle of the Sulu Sea. It is a bit closer to Negros Occidental than to Palawan Island. Cagayancillo is the closest settlement to the Tubbataha Reefs Natural Park.
The word Cagayancillo is Spanish meaning "Little Cagayan".
It is the smallest municipality in Palawan; land area is only 2,639 hectares (6,520 acres), and as of 2020, its population was just under 7,000.
The municipality is composed of 31 islands and islets.
The municipality is exposed to both monsoons. The Amihan or north-east winds blow from November to March while the Habagat or south-west winds visit the area from June to October. The summer months from April to June receive the moderate daplak wind from the north-west.
- Cagayancillo Fort is one of the surviving defense forts in Palawan built during the Spanish Colonial Period. Work on the fort was started in the late 16th century, but it was not completed till the early 18th century, spanning almost 130 years. The 162-m² (1,740-sq ft) diamond-shaped fort was built on the coast on a high point on the island and made from sea rocks mixed with lime. Like some of the other Spanish forts in this area, inside is a church surrounded by its massive 12-m-high (39 ft) and 3-m-thick (9.8 ft) walls, providing a safe place for the residents during marauding pirate attacks. The other Spanish Colonial fortifications in Palawan are Fort Santa Isabel in Taytay and Cuyo Fort in Cuyo.