The Roman Catholic Diocese of San Marcos (erected 10 March 1951) is a suffragan diocese of the Archdiocese of Los Altos Quetzaltenango-Totonicapán.
Bishops
Ordinaries
- Celestino Miguel Fernández Pérez, OFM (1955–1971)
- Próspero Penados del Barrio (1971–1983), appointed Archbishop of Guatemala
- Julio Amílcar Bethancourt Fioravanti (1984–1988), appointed Bishop of Huehuetenango
- Álvaro Leonel Ramazzini Imeri (1988–2012), appointed Bishop of Huehuetenango on 14 May 2012; future Cardinal
- Carlos Enrique Trinidad Gómez (2014–2018)
- Bernabé de Jesús Sagastume Lemus, OFMCap (2021–present)
Auxiliary bishops
- Próspero Penados del Barrio (1966–1971), appointed bishop
Other priest of this diocese who became bishop
- Félix Eduardo Antonio Calderón Cruz, appointed Bishop of San Francisco de Asís de Jutiapa in 2016
Territorial losses
| Year | Along with | To form |
|---|---|---|
| 1961 | Territorial Prelature of Huehuetenango |