| Jurisdiction: | Diocese |
| Alajuela | |
| Latin: | Dioecesis Alaiuelensis |
| Local: | Diócesis de Alajuela |
| Country: | Costa Rica |
| Metropolitan: | Hugo Barrantes Ureña |
| Province: | Province of San José de Costa Rica |
| Area Km2: | 2,700 |
| Population: | 662,520 |
| Population As Of: | 2006 |
| Catholics: | 551,100 |
| Catholics Percent: | 83.2 |
| Parishes: | 31 |
| Denomination: | Catholic Church |
| Sui Iuris Church: | Latin Church |
| Rite: | Roman Rite |
| Established: | 16 February 1921 (years ago) |
| Bishop Title: | Bishop |
| Bishop: | Bartolomé Buigues Oller, T.C. |
| Emeritus Bishops: | Angel San Casimiro Fernandez, O.A.R. |
| Map: | Costa Rica - Diocesi di Alajuela.jpg |
The Diocese of Alajuela (la|Dioecesis Alaiuelensis) is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Costa Rica. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of San José de Costa Rica. The Diocese of Alajuela was erected on 16 February 1921.
| Year | Along with | To form | |
|---|---|---|---|
| 1954 | Diocese of San Isidro de El General | ||
| 1961 | Diocese of Tilarán | ||
| 1995 | Diocese of Ciudad Quesada |