John Lynch (pseudonym: Gratianus Lucius; c. 1599 – c. 1677) was an Irish Roman Catholic priest, known as a historian and Archdeacon of Tuam.
He was born into a Hiberno-Norman family at Galway, probably in 1599; according to tradition his father was Alexander Lynch, a schoolmaster.
He celebrated Mass in secret, and in private houses; and kept a school.
[1] He was appointed archdeacon of Tuam, and lived in the old castle of Ruaidrí Ua Conchobair.
On the surrender of Galway to the New Model Army in 1652 he left for France; some of his works were printed at St. Malo.