Zachlumia or Zachumlia , also Hum, was a medieval principality located in the modern-day regions of Herzegovina and southern Dalmatia (today parts of Bosnia and Herzegovina and Croatia, respectively). In some periods it was a fully independent or semi-independent South Slavic principality. It maintained relations with various foreign and neighbouring powers (Byzantine Empire, First Bulgarian Empire, Kingdom of Croatia, Principality of Serbia) and later was subjected (temporarily or for a longer period) to Kingdom of Hungary, Kingdom of Serbia, Kingdom of Bosnia, and at the end to the Ottoman Empire.