From its inception in 1118 through 1596, the Kingdom of Desmond was ruled by the family of the MacCarthy Mór, (i.e., the "Great MacCarthy"). For centuries the MacCarthy Mórs reigned as Kings of Desmond, and maintained significant demesne lands (manors) throughout the kingdom. Principal seats were at Pallis Castle (near present-day Killarney), Castle Lough (on Killarney's Lough Leane), and Ballycarbery Castle (near Caherciveen on the Ring of Kerry).
After the death of King Donal IX MacCarthy Mór in 1596, and following the effective end of the Gaelic Order after the Battle of Kinsale (1602), the former Kingdom of Desmond was partitioned between County Cork and County Kerry (in 1606).
Subsequent to the end of the MacCarthy Mór sovereignty in Desmond, descendants entitled to the highest Gaelic designation of "Chief of the Name" of the MacCarthy Mór family, are also properly styled as Princes of Desmond. A secondary title of the MacCarthy Mór would derive from the lordship designation of his Sept.
Generational offshoots (cadet family lines) of the Royal House of Desmond received their own territories and titles – known as appanages of the royal house. Those MacCarthy Mór cadet branches which did not evolve to the MacCarthy Mór chief-of-the-name status, became chiefs-of-the-name of their own princely septs, i.e. MacCarthy Reagh of Carbery, MacCarthy of Muskerry, and MacDonough MacCarthy of Duhallow.
Because of their location, it was the MacCarthys of Muskerry and Carbery who ended up fighting the majority of the battles against the Normans – mainly the FitzGerald Earls of Desmond – while defending and expanding the Gaelic realms. By the mid-sixteenth century, the main line of the MacCarthys Mor had largely withdrawn to Kerry, so any modern claims that they are still entitled to the nominal overlordship of Carbery and Muskerry might be rejected by any extant descendants of these branches.