The legislative districts of Cagayan are the representations of the province of Cagayan in the various national legislatures of the Philippines. The province is currently represented in the lower house of the Congress of the Philippines through its first, second, and third congressional districts.

Cagayan, which included the sub-province of Batanes, was initially divided into two representative districts in 1907. Batanes was last represented as part of the province's first district in 1909, after its re-establishment as a province by virtue of Act No. 1952 enacted on May 20, 1909, warranted its separate representation. A minor adjustment of district boundaries, mandated by Act No. 3032 enacted on March 19, 1922, took effect starting in the 1922 elections.

When seats for the upper house of the Philippine Legislature were elected from territory-based districts between 1916 and 1935, Cagayan formed part of the first senatorial district which elected two out of the 24-member senate. However, residents of two towns that had been annexed from Mountain Province — Allacapan (1928) and Langangan (1922) — were not extended the right to vote in assembly or senatorial elections until 1935, after the passage of Act No. 4203 placed them in the second district of Cagayan.^[1]

By virtue of Executive Order No. 84 issued by Philippine Executive Commission Chairman Jorge Vargas on August 31, 1942, the province of Batanes was abolished and its territory was placed under Cagayan's jurisdiction for the duration of the Second World War. Two delegates represented the province in the National Assembly of the Japanese-sponsored Second Philippine Republic: one was the provincial governor (an ex officio member), while the other was elected through a provincial assembly of KALIBAPI members during the Japanese occupation of the Philippines. Upon the restoration of the Philippine Commonwealth in 1945, the province retained its two pre-war representative districts, and Batanes was once again represented separately.

The province was represented in the Interim Batasang Pambansa as part of Region II from 1978 to 1984, and elected two representatives, at large, to the Regular Batasang Pambansa in 1984. Cagayan was reapportioned into three congressional districts under the new Constitution^[2] which was proclaimed on February 11, 1987, and elected members to the restored House of Representatives starting that same year.

• Municipalities: Alcala, Aparri, Baggao, Buguey, Camalaniugan, Gattaran, Gonzaga, Lal-lo, Santa Ana, Santa Teresita
• Population (2020): 459,819^[3]

• Municipalities: Abulug, Allacapan, Ballesteros, Calayan, Claveria, Lasam, Pamplona, Piat, Rizal, Sanchez-Mira, Santa Praxedes, Santo Niño
• Population (2020): 322,634^[3]

Notes

• City: Tuguegarao (became city 1999)
• Municipalities: Amulung, Enrile, Iguig, Peñablanca, Solana, Tuao
• Population (2020): 486,150^[3]

Notes

• Legislative district of Batanes
• Legislative district of Mountain Province