John de Cogan was an Anglo-Irish knight who lived in the period between 1220 and 1278.
In the 1230s he led a contingent from Munster which participated in the conquest of Connacht under Richard Mor de Burgh.
On the death of his father-in-law, Gerald Prendergast, in 1261, he inherited some of his estates in right of his wife.
In 1263 he was involved in a land dispute between Walter, Earl of Ulster, and Maurice FitzGerald.
We may suspect that an estate hereabouts {in the barony of Tirawley} passed like Castlebar from a de Barry to a Cogan.