Seán Mac Giollarnáth (1880-29 January 1970) was an Irish folklorist.
A native of Coill an Bhogaigh, Gurteen, Ballinasloe, Mac Giollarnáth lived for a time in London before moving to Dublin where he taught at St. Enda's, Rathfarnham.
In 1923 he was appointed District Justice, which he held till he retired in 1950.
He held a lifelong interest in wildlife and folklore, which formed the basis for much of his published work.
He was awarded an LL.D by the National University of Ireland in the 1960s.