Mapun, officially the Municipality of Mapun (Tagalog: Bayan ng Mapun), is a municipality in the province of Tawi-Tawi, Philippines. According to the 2020 census, it has a population of 30,038 people.

It was formerly known as Cagayan de Sulu until 1984, then as Cagayan de Tawi-Tawi until 1988.

Mapun is an island municipality in the Sulu Sea on the south-western extreme of the Philippines, located very close to Sabah, Malaysia as well as to Palawan. The people inhabiting the island are known as Jama Mapun or "people of Mapun". Their local language is Pullun Mapun, which means "Mapun language".

Due to an administrative error in the Treaty of Paris, while the remainder of the Philippines was ceded to the United States, Sibutu and Cagayan de Sulu were retained under Spanish Sovereignty until they were formally ceded to the United States upon the ratification of the Treaty of Washington on March 23, 1901. In 1946, the Philippines became an independent country, including Mapun island as part of it.

Cagayan de Sulu was among the islands in the Sulu Archipelago being occupied by the Samal people (Sama-Bajau) in the late 18th and early 19th century. The island likewise had a smaller Tausug population than Palawan.

In 1783, an East India Company ship, the Antelope, spent a month trading among Cagayan de Sulu and the Tapian Tana islands.

Cagayan de Sulu was among the traditional sources of rice and sago. In the 1790s, rice was extensively cultivated for export. The products once supplied the Tausugs in Sulu.

In 1872, as Spanish authorities began conquering Jolo, they issued a regulation aiming to destroy all Tausug shipping, in a move to reduce their trading activities to a mere submission. Despite this, a usual number of prahus (trading boats) from southern Palawan and Cagayan de Sulu continued to go to the British settlement.