If you want to get into Classic Christianity, then the Church Fathers are essential! These are the theologians, liturgists, monks, et al, who lived in the first centuries of Christianity and helped work through the major doctrines of the faith, establish church order & canon law, see the formation of the New Testament canon and much more!
Below are primarily English language resources, although at the very end I give links to them in the original where available. First are some more general websites, then where to find Latin Fathers, then Greek Fathers, then Syriac & Coptic resources. I have set aside liturgies for the moment; prayer resources will find their own page in due course. In the interests of something akin to brevity, we end ‘the Fathers’ with the typical choices of John of Damascus (d. 749) in the East, and Isidore of Seville (d. 636) in the West. I hope to maintain this page as time goes on — feel free to direct me to sources not otherwise listed! Remember, though, if I know it is included in the ‘General Internet Resources’, I won’t list it separately.
General Internet Resources
The Ante-Nicene Fathers & Nicene and Post-Nicene Fathers. This is the most common series of the Church Fathers, from the Victorian era. The link is to the Christian Classics Ethereal Library, but the content is the same as at New Advent. Here you can find the major Fathers such as Ignatius of Antioch, Tertullian, Origen, Augustine of Hippo, John Chrysostom, Ambrose of Milan, and many more.
Early Church Fathers – Additional Texts. Roger Pearse has put together a vast resource of public domain translations of Church Fathers not available in the abovementioned ANF and NPNF. Here you will find luminaries lacking from the other series, such as Cyril of Alexandria, Epiphanius of Salamis, and Salvian of Marseille, as well as more of many great Fathers such as Irenaeus, Ambrose, Origen, and others, and people you may never have heard of such as Philostorgius, Zachariah of Mitylene, or Severus of Antioch. Many of the texts here are as important as those mentioned above.
Monachos: Patristic Source Texts. Monachos’ tagline is ‘Orthodoxy Through Patristic, Monastic, and Liturgical Study.’ Here you will find a large variety of patristic texts; some are repeats from above, but not all. Since so many of the earliest sources are repeated throughout the internet (including this site), Monachos is an especially great resource for later Fathers, mainly East but also West. Come here for sources surrounding the Sixth Ecumenical Council, such as the Letter of Pope Agatho; or come here for St Andrew of Crete, Boethius, Cassiodorus, bits of Cyril not at tertullian.org, Gregory the Great’s Moralia in Job, Jacob of Serug, John Moschus, Macarius of Egypt, Maximus the Confessor, and many more! Only a few eastern Fathers not found above managed to miss being here!
Early Christian Writings. This website provides texts from the first three centuries of Christianity, with an emphasis on apocrypha and Gnostic texts. Worth perusing for another angle on ancient Christianity that you won’t get from the sites mentioned above!
Patrologia Syriaca and Patrologia Orientalis Online. The Patrologia Syriaca gives Syriac texts with Latin translation in two volumes. The Patrologia Orientalis gives ancient and medieval Christian texts in Syriac, Coptic, Arabic, Armenian, Ethiopian, and some in Greek, from the Middle East, in the original with translation into a modern language, often French, not infrequently English. This is, once again, the work of Roger Pearse. He has both volumes of PS, but for PO only 2, 3, 6-19, 21-23, and 25, after which I doubt they are in the public domain. Some of volumes he lacks are available on archive.org; I shall list them below with Syriac & Coptic Fathers. Oriental Fathers of interest herein are Severus of Antioch (PO 6, 8, 12, 14, 22, 23, 25) and John of Ephesus (PO 17-19).
These are not to be neglected. If you are a member of a university library, check your library’s database for series of texts to which they may have a subscription. One such is the Works of Saint Augustine that provides an English translation of almost everything, if not everything, the great Latin Father wrote.
Another subscription with broader interest is the Liverpool University Press series Translated Texts for Historians. This series provides translations of Late Antique and Early Medieval texts, many of them patristic in nature, including Ambrose of Milan, Venantius Fortunatus, sources from the Syrian school at Nisibis, Cassiodorus, Gregory of Tours, Orosius, much Bede, Evagrius Scholasticus, and the Acts of the Councils of Chalcedon and Constantinople.
Also worth reading is the blog Enlarging the Heart, where Mark Armitage provides a classic Christian reading every day, very often from the Church Fathers.
An conceptually interesting book (that I’ve not actually read) is Fathers of the Church by Topic — a topically-arranged anthology.
Latin Fathers Online
Victorinus of Poetovio (d. 304). In Apocalypsin. Commentaries on Revelation are rare, so this is worth a look. Furthermore, this is a complete translation of all of Victorinus’ text, unlike the version at the CCEL up above.
Ausonius (310-395). The Daily Round, III: The Prayer. Although he is not usually considered amongst the Church Fathers, this prayer of Ausonius is quite beautiful. See also his ‘Easter Verses.’ Loeb Classical Library.
Egeria (380s). The Pilgrimage. Egeria (in some versions Aetheria) is one of our only ‘Church Mothers’. She seems to have been a Spanish nun or religious woman of some sort. In the 380s she went on pilgrimage/spiritual tourism in the Holy Land and wrote about it.
Prudentius (348-413). Poems, Vol. 1. Loeb Classical Library. This and vol. 2 below are all you need, although I give other translations.
—. Poems, Vol 2. Loeb Classical Library.
Caelius Sedulius (5th c.) The Easter Song. (Carmen Paschale.)
Prosper of Aquitaine (390-455). The Call of All Nations.
Patrick of Ireland (c. 373 – c. 463). St Patrick: His Writings and Life. The Life is that of Muirchu (7th c)
Benedict of Nursia (c. 480-543). The Rule of St Benedict.
Boethius (480-524). The Theological Tractates and Consolation of Philosophy.
Avitus of Vienne (494-523). The Poems of Alcimus Ecdicius Avitus.
Gregory of Tours (538-594). History of the Franks. Substantial selections of Gregory’s history.
Venantius Fortunatus (530-609). The best online resource I have found for him is his author page at hymnary.org.
Columbanus (543-615). Letters of Columbanus.
Isidore of Seville (560-636). “The last of the Latin Fathers”, only his Chronicon is available through Roger Pearse, More Fathers.
—. The Etymologies. (In Latin.)
Greek Fathers Online
Hippolytus of Rome (d. 235). The Apostolic Tradition. This is one of our earliest surviving liturgical texts, and in it we see how much survives into the liturgy of today.
Athanasius of Alexandria (introduction, d. 373), Theodoret of Cyrrhus (notes, d. 457), Bernard of Clairvaux (appendix, d. 1153). The Song of Songs Translated into English Verse. This looks like an interesting experiment!
Athanasius of Alexandria (d. 373). Commentary on Psalms 22 and 86.
Ephraim the Syrian (d. 373), Greek texts attributed to him. Trans. Ephrem Lash. Sermon in Heptasyllablics
—. Three Short Discourses
—. 55 Beatitudes
—. To the Monks of Egypt
—. On the Departed Fathers
—. On Abraham and Isaac
—. On Joseph
—. On the Transfiguration
—. On The Passion
Evagrius Ponticus. Father Luke Dysinger has working translations (not always complete) with Greek text of:
—. Kephalaia Gnostica
—. Peri Logismon (On Thoughts)
—. On Prayer
—. On Psalms.
—. On Proverbs
—. On Ecclesiastes
—. On Job
—. Father Theophanes has translations at The Evagrian Ascetical System of Treatise on the Practical Life, On the Thoughts, Gnostikos, Kephalaia Gnostica, and Skemmata.
Hesychius the Priest. On Sobriety.
Ps.-Macarius the Egyptian. Fifty Spiritual Homilies.
Ps.-Dionysius the Areopagite. Part 1: Divine Names, Mystic Theology, Letters, etc.
Ps.-Dionysius the Areopagite. Part 2: The Heavenly Hierarchy and The Ecclesiastical Hierarchy
Romanos the Melodist (mid-6th c). Kontakia 16, 20, 22, 32, 49, 51, Akathist. Trans. Ephrem Lash.
John Climacus (‘of the Ladder’, 525-606). The Ladder of Divine Ascent.
Syriac and Coptic Fathers Online
Pachomius, Rule. (Translated from the Ethiopic.)
Isaac the Syrian (of Nineveh). Mystic Treatises. One of the most famous Syriac Fathers, whose ascetical and mystical works are an inspiration to many Orthodox to this day; this text is also known as the Ascetical Homilies.
Miscellaneous Coptic Texts in the Dialect of Upper Egypt. Ed. and trans. by E. A. Wallis Budge, including works (among others) by Theodore of Antioch, Cyril of Jerusalem, Demetrius of Antioch, Epiphanius of Salamis, Severus of Antioch, and John Chrysostom.
Patrologia Orientalis, Vol 1. Mostly French translations; in English is the History of the patriarchs of the Coptic church of Alexandria (S. Mark to Benjamin I)
Patrologia Orientalis, Vol. 4. Although this volume is mostly French, I draw the reader’s attention to Severus of Antioch’s “Homilies Cathedrales”.
Patrologia Orientalis, Vol. 5, fascicle IV. Kitab al-`unvan = Histoire universelle, écrite par Agapius (Mahboub) de Menbidj
Although through subscription via your university library website, be aware of the Patrologia Latina Database, the Acta Sanctorum, the Library of Latin Texts A & B, and the Thesaurus Linguae Graecae, all of which have large quantities of original language material of the Fathers available.
Patrologia Latina has been digitised, and there is a growing body of other patristic material in Latin, Greek, Syriac, and Coptic available online as editions out of copyright are digitised by various bodies.