The Kingdom of Mercia (Old English: Miercna rīce), usually referred to as Mercia /ˈmɜrsiə, ˈmɜrʃə/, was one of the kingdoms of the Anglo-Saxon Heptarchy. The name is a Latinisation of the Old English Mierce or Myrce, meaning "border people" (see March).The kingdom was centred on the valley of the River Trent and its tributaries, in the region now known as the English Midlands.