Acta Sanctorum Hiberniae
Aided by Father Hugh Ward, O.F.M., Father Stephen White, S.J., and Brother Míchél Ó Cléirigh, O.F.M., Colgan sedulously collected enormous material for the Lives of the Irish Saints, and at length, after thirty years of sifting and digesting his materials, put to press his Acta Sanctorum Hiberniae, a portion of the expense of which was defrayed by Archbishop O'Reilly of Armagh.
The first volume, covering 270 lives of Irish saints (except Brigid and Patrick) for the months of January, February, and March, was intended to be the third volume of the Ecclesiastical Antiquities of Ireland, but only one volume was printed at Leuven in 1645.
- The full title runs as follows: Acta Sanctorum veteris et majoris Scotiae, seu Hiberniae, Sanctorum Insulae, partim ex variis per Europam MSS. codd. exscripta, partim ex antiquis monumentis et probatis authoribus eruta et congesta; omnia notis et appendicibus illustrata, per R.P.F. Joannem Colganum, in conventu F.F. Minor. Hibern. Scrictioris Observ., Lovanii, S. Theologiae Lectorem Jubilatum. Nunc primum de eisdem actis juxta ordinem mensium et dierum prodit tomus primus, qui de sacris Hiberniae antiquitatibus est tertius, Januarium, Februarium, et Martium complectens.
- John Colgan, The 'Acta sanctorum Hiberniae' of John Colgan, reproduced at the Ordnance Survey, Dublin. Reflex facsimiles, Irish Manuscript Commission 5. Dublin: Ordnance Survey, 1948. 906 pp. Facsimile edition of the book (Leuven: De Witte, 1645), with an introduction by Brendan Jennings.