The Diocese of Alajuela (Latin: 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.
Bishops
Ordinaries
- Antonio del Carmen Monestel Zamora (1921–1937)
- Víctor Manuel Sanabria Martínez (1938–1940), appointed Archbishop of San José de Costa Rica
- Juan Vicente Solís Fernández (1940–1967)
- Enrique Bolaños Quesada (1970–1980)
- José Rafael Barquero Arce (1980–2007)
- Angel San Casimiro Fernandez, O.A.R. (2007–2018)
- Bartolomé Buigues Oller, T.C. (2018- )
Auxiliary bishops
- Enrique Bolaños Quesada (1962–1970), appointed Bishop here
- José Rafael Barquero Arce (1979–1980), appointed Bishop here