Mac Raghnaill is a masculine surname in the Irish language.

The name translates into English as "son of Raghnall".

The surname originated as a patronym, however it no longer refers to the actual name of the bearer's father.

The name Raghnall is a Gaelic derivative of the Old Norse personal name Røgnvaldr / Rǫgnvaldr / Rögnvaldr.

[1] These three surnames can be Anglicised variously as: Grannell, MacRanald, MacRandell, MacCrindle, MacReynold, MacReynolds, Randalson, Rondalson, Reynoldson, Rannals, Randals, Randles, Ranolds, and Reynolds.