Calayan, officially the Municipality of Calayan (Ilocano: Ili ti Calayan; Ivatan: Kavahayan nu Calayan; Ibanag: Ili nat Calayan; Tagalog: Bayan ng Calayan), is a municipality in the province of Cagayan, Philippines. According to the 2024 census, it has a population of 18,008 people.

It is home to the Calayan rail, a flightless bird identified as a separate species in 2004 and endemic to Calayan Island.

The municipality's name in the Ibanag language literally means "where laya (ginger) abounds".

While Calayan was officially conquered by the Spanish starting in 1619, authorities were only able to maintain a sporadic presence in the area due to its isolated location. It was taken over by the Americans in 1900. In the 1920s, it was briefly placed under the jurisdiction of Aparri after a clerk ran off with the municipal treasury's funds.

Calayan is located in the Luzon Strait north of Luzon Island and south of Taiwan via Bashi Channel to Luzon Strait. The town is composed of four of the five major islands of the Babuyan Islands namely: Calayan, Camiguin, Dalupiri and Babuyan Island. Calayan Island is the largest of the Babuyan Islands. Fuga Island, the fifth island within the Babuyan Islands, is part of Aparri municipality despite being closer to Claveria.

Calayan Island is located about 24 miles (39 km) west-south-west of Babuyan Island off the north coast of the Philippines and belongs to the Babuyan Islands group in the China Sea. The island is hemmed between Aparri and Batanes islands and it is larger than the Fuga Island, which is 25 miles (40 km) away. It is the second district in the province of Cagayan and its 29th municipality.

Calayan is situated 207.75 kilometres (129.09 mi) from the provincial capital Tuguegarao, and 692.90 kilometres (430.55 mi) from the country's capital city of Manila.

Calayan is politically subdivided into 12 barangays. Each barangay consists of puroks while some have sitios.