Zachlumia or Zahumlje,also Hum, is a medieval principality located in the modern-day regions of Herzegovina and southern Dalmatia (today parts of Bosnia and Herzegovina and Croatia, respectively).

While sometimes a fully independent or semi-independent Slavic entity, Zahumlje is mainly under foreign powers; the Byzantine Empire, Kingdom of Croatia, Kingdom of Serbia, Kingdom of Hungary, Kingdom of Bosnia and at the end under the Ottoman Empire.