Alajuela is a province of Costa Rica. It is located in the north-central part of the country, bordering Nicaragua to the north, and clockwise the provinces Heredia, San José, Puntarenas and Guanacaste. The province covers an area of 9,757.53 km², and has a population of 767,143.

The capital is Alajuela, other important cities include Ciudad Quesada.