The MacCarthy dynasty of Muskerry is a branch of the great MacCarthy Mor dynasty, the Kings of Desmond. Their branch descends from Dermod Mor MacCarthy, 1st Lord of Muscry (1310-1367/8), second son of Cormac MacCarthy Mor (1271–1359), King of Desmond.
Dermod Mor was created Lord of Muscry (Muskerry, along the Lee river in central County Cork) in 1353. His descendant Cormac Oge MacCarthy, 17th Lord of Muscry, was in 1628 created Charles MacCarty, 1st Viscount Muskerry, and his son, the 2nd Viscount Muskerry, was in 1658 created Donough MacCarty, 1st Earl of Clancarty.
The dynasty is still in existence and can be considered to still broadly belong to the Irish nobility, but its leadership is in confusion. There also remains some dispute with their (friendly) rivals and kinsmen the MacCarthys Reagh, concerning the title Prince of Desmond. The late main line of the MacCarthy Mor dynasty became extinct in the late 16th century and it has ever since been unclear who inherits the title, because of the advent of the career of Florence MacCarthy. See Kingdom of Desmond. There are also earlier MacCarthy Mor septs in existence who are claimants. The situation was recently thrown into even more exotic confusion by the impostor Terence Francis MacCarthy.