Alajuela is one of the seven multi-member constituencies of the Legislative Assembly, the national legislature of Costa Rica. The constituency was established in 1949 when the Legislative Assembly was established by the modified constitution imposed by the Figueres dictatorship. It is conterminous with the province of Alajuela. The constituency currently elects 11 of the 57 members of the Legislative Assembly using the closed party-list proportional representation electoral system. At the 2022 general election it had 679,844 registered electors.