In Christianity, minor orders are ranks of church ministry. In the Catholic Church, the predominating Latin Church formerly distinguished between the major orders —priest, deacon and subdeacon—and four minor orders—acolyte, exorcist, lector, and porter. In 1972, the Vatican re-titled the minor orders as "ministries", with those of lector and acolyte being kept throughout the Latin Church. In the Eastern Orthodox Church, the three minor orders in use are those of subdeacon, reader and chanter.

An ostiarius, a Latin word sometimes anglicized as ostiary but often literally translated as porter or doorman, originally was an enslaved person or guard posted at the entrance of a building, similarly to a gatekeeper.