Donlevy is a surname of Irish origin. Also spelt as MacDonlevy, Donleavy, Dunleavy, and MacAleavey, it derives from the Irish Mac Duinnshléibhe, meaning "brown mountain". Ó Duinnshléibhe is a variant Irish spelling. Their eponymous ancestor is Donn Sléibe mac Echdacha, who ruled as king of the Irish petty-kingdom of Dál Fiatach, as well as its over-kingdom, Ulaid, in the late 10th century. In the aftermath of John de Courcy's conquest of Ulaid in 1177, some of the dynasty migrated to present-day County Donegal in the Republic of Ireland, whilst others went to Scotland. In Donegal they became the hereditary physicians (Old Irish: ollahm leighis) of the Cenél Conaill of Tír Conaill.
After the Battle of Kinsale in 1602, the sept migrated to the province of Connacht, where their name is now most common. Some MacDonlevy's in Donegal adopted the surname Mac an Ultaigh, meaning "son of the Ulsterman", which was anglicised as MacAnulty and MacNulty.
This is a partial list, based on the Irish annals of members of the MacDonlevy and McNulty physicians of the Cenél Conaill of Tír Conaill.
The Annals note further that the branch of the MacDonlevy, who had been the physicians, still existed near Kilmacrenan, County Donegal in the early 17th century.
Tradition is that the MacDonlevy physicians educated in the medical arts Tír Conaill native Niall Ó Glacáin (Latinised as Nellanus Glacanus). Glacanus became a famed physician, professor of medicine and medical researcher at the University of Bologna.