John Fergus was an Irish physician and man of letters, c.1700 – c.1761.
A descendant of the ÃÂ Fearghuis medical family of Connacht, Doctor Fergus a native of County Mayo but moved to Dublin city early in his adult life.
He was a scribe, and book collector, as well as a member of the àNeachtáin literary circle in early 18th century Dublin. He amassed a huge library of Irish manuscripts, which included the Liber Flavus Fergusiorum, a medical text created by his ancestors in the 14th century.