Databases & Maps
Clauss-Slaby epigraphic database – non-Christian inscriptions from Rome
http://www.manfredclauss.de/
Cult of Saints Database Oxford
http://csla.history.ox.ac.uk/
Epigraphic Database Bari (EDB) – Christian Inscriptions from Rome
https://www.edb.uniba.it/
Digital Atlas of the Roman Empire (DARE)
https://dh.gu.se/dare/ and https://imperium.ahlfeldt.se/
Digital Atlas of the Roman Empire 2.0
https://klokantech.github.io/roman-empire/
Index of Medieval Art – formerly Index of Christian Art, Open Access after 31.05.2023
https://theindex.princeton.edu/
Lexicon of Greek Personal Names
http://clas-lgpn5.classics.ox.ac.uk
ORBIS: The Stanford Geospatial Network Model of the Roman World
https://orbis.stanford.edu/
Oxford Roman Economy Project
http://oxrep.classics.ox.ac.uk/
Pleiades – community-built gazetteer and graph of ancient places
https://pleiades.stoa.org/
Presbyters in the Late Antique West
http://presbytersproject.ihuw.pl/
Tertullian Project – Large collection of material
https://www.tertullian.org/
Trismegistos – database for ancient places, names, epigraphy, papyri and a lot more
https://www.trismegistos.org/
Search tools
Annoted Patristic journal bibliography (BIBP) of the Université Laval
http://www4.bibl.ulaval.ca/bd/bibp/
Clavis Patrum – standard reference database for Patristic, Medieval and Byzantine texts
https://clavis.brepols.net/
Reires Search – collections of manuscripts, documents, and rare books of Christian, Jewish and Muslim works
https://reiresearch.eu/
RI OPAC – literature database for medieval (and Late Antique) research covering all disciplines
http://opac.regesta-imperii.de/
Reference works
Encyclopedia of Ancient Christianity. Edited by Angelo Di Berardino, Thomas C. Oden, and James Hoover,. Downers Grove: InterVarsity Press, 2014. (A03:27 ENCY) – Standard, mostly up to date reference work specialised on Christianity in Antiquity. Always a good point of departure.
Religion Past & Present: Encyclopedia of Theology and Religion. Edited by Dieter Betz, Don S. Browning, Bernd Janowski, and Eberhard. Jüngel. Leiden: Brill, 2007. (A03:2 RELI) – High quality generic reference work on (historical) theology and religion.
Reallexikon für Antike und Christentum. Stuttgart: Hiersemann, 1950- (A03:27 REAL) – One of the best reference work for ancient Christianity in context of Antiquity and Judaism. Volumes before 1990 are often outdated, but the references to primary sources are still very valuable.
Enciclopedia dei Papi. Edited by Manlio Simonetti, Giulia Barone, and Massimo Bray. Roma: Istituto della Enciclopedia Italiana, 2000. (A270.010.4 ENCI and online: https://www.treccani.it/enciclopedia/elenco-opere/Enciclopedia_dei_Papi) – All you (n)ever wanted to know about individual bishops of Rome/popes including primary sources. Often very high scientific quality.
Dictionnaire d’histoire et de géographie ecclésiastiques. Paris: Letouzey et Ané, 1909- (A03:27 DICT and online from KU Leuven) – One of the most eminent ancient Christianity encyclopedia, which was never finished. Apart from the recently updated entries, the lexicon is largely outdated, but it still an excellent source of inspiration and of primary sources because of its eminency.