The Order of Saint John (Knights of Malta, Knights Hospitaller) was organised in a system of commanderies during the high medieval to early modern periods, to some extent surviving as the organisational structure of the several descended orders that formed after the Reformation.
In the Late Middle Ages, the bulk of possessions of the order were in the Holy Roman Empire, France, Castile, Aragon and Portugal, but they extended into Poland, Hungary, southern Italy, England and Denmark, with individual outliers in Ireland, Scotland, Sweden and Greece (the main seat of the order was in Rhodes from 1310 until 1522, and in Malta from 1530 until 1798).