Philippines's 1st senatorial district

Philippines's 1st senatorial district, officially the First Senatorial District of the Philippine Islands (Primer Distrito Senatorial de las Islas Filipinas), was one of the twelve senatorial districts of the Philippines in existence between 1916 and 1935. It elected two members to the Senate of the Philippines, the upper chamber of the bicameral Philippine Legislature under the Insular Government of the Philippine Islands for each of the 4th to 10th legislatures. The district was created under the 1916 Jones Law from the northern Luzon provinces of Batanes, Cagayan, Ilocos Norte, Ilocos Sur and Isabela. Abra was added in 1917 upon its re-establishment as a regular province separate from Ilocos Sur.

The district was represented by a total of six senators throughout its existence. It was abolished in 1935 when a unicameral National Assembly was installed under a new constitution following the passage of the Tydings–McDuffie Act which established the Commonwealth of the Philippines. Since the 1941 elections when the Senate was restored after a constitutional plebiscite, all twenty-four members of the upper house have been elected countrywide at-large. It was last represented by Elpidio Quirino and Melecio Arranz of the Nacionalista Democrático.