Early Christian inscriptions are the epigraphical remains of early Christianity. They are a valuable source of information in addition to the writings of the Church Fathers regarding the development of Christian thought and life in the first six centuries of the religion's existence. The three main types are sepulchral inscriptions, epigraphic records, and inscriptions concerning private life.

The materials on which early Christian inscriptions were written were the same as those used for other inscriptions in antiquity. For sepulchral inscriptions and epigraphic records, the substance commonly employed was stone of different kinds, native or imported. The use of metal was less common. When the inscription is properly cut into the stone, it is called a titulus or marble; if merely scratched on the stone, the Italian word graffito is used; a painted inscription is called dipinto, and a mosaic inscription—such as those found largely in North Africa, Spain, and the East—are called opus musivum. It was a common practice in the Greco-Roman world to make use of slabs already inscribed, that is, to take the reverse of a slab already used for an inscription for the inscribing of a Christian one; such a slab is called an opisthograph.

The form of the Christian inscriptions does not differ from that of the non-Christian inscriptions that were contemporary with them, except when sepulchral in character, and then only in the case of the tituli of the catacombs. The forms of stone sepulchral inscriptions differ in the Greek East and Latin West. The most common form in the East was the upright "stele" (Greek: στήλη, a block or slab of stone), frequently ornamented with a fillet or a projecting curved moulding; in the West a slab for the closing of the grave was often used. Thus the majority of the graves (loculi) in the catacombs were closed with thin, rectangular slabs of terracotta or marble; the graves called arcosolia were covered with heavy, flat slabs, while on the sarcophagi a panel (tabula) or a disk (discus) was frequently reserved on the front wall for an inscription.

The majority of the early Christian inscriptions, viewed from a technical and paleographical standpoint, give evidence of artistic decay: this applies especially to the tituli of the catacombs, which are, as a rule, less finely executed than the non-Christian work of the same time. A striking exception is formed by the Damasine letters introduced in the 4th century by Furius Dionysius Filocalus, the calligraphist of Pope Damasus I. The other forms of letters did not vary essentially from those employed by the ancients. The most important was the classical capital writing, customary from the time of Augustus; from the 4th century on it was gradually replaced by the uncial writing, the cursive characters being more or less confined to graffito inscriptions.

Latin inscriptions are the most numerous. In the East, Greek was commonly employed, interesting dialects being occasionally found, as in the Christian inscriptions from Nubia in southern Egypt that were deciphered in the 19th century. Special mention should also be made of the Coptic inscriptions. The text is very often shortened by means of signs and abbreviations. At any early date, Christian abbreviations were found side by side with those traditionally used in connection with the religions of the Roman Empire. One of the most common was D.M. for Diis Manibus, "to the protecting Deities of the Lower World." The phrase presumably lost its original religious meaning and became a conventional formula as used by the early Christians. Most of the time, dates of Christian inscriptions must be judged from context, but when dates are given, they appear in Roman consular notation, that is, by naming the two consuls who held office that year. The method of chronological computation varied in different countries. The present Dionysian chronology does not appear in the early Christian inscriptions.

The earliest of these epitaphs are characterized by their brevity, only the name of the dead being given. Later a short acclamation was added, such as "in God" or "in Peace." From the end of the 2nd century, the formulae were enlarged by the addition of family names and the date of burial. In the third and fourth centuries, the text of the epitaphs was expanded with the age of the deceased, the year (reckoned according to the consuls in office), and laudatory epithets. For these particulars each of the regions comprising the Roman Empire had its own distinct expressions, contractions, and acclamations.

Large use was made of symbolism. Thus the open cross is found in the epitaphs of the catacombs as early as the 2nd century, and from the 3rd to the 6th century the monogrammatic cross in its various forms appears as a regular part of the epitaphs. The cryptic emblems of primitive Christianity are also used in the epitaphs: the fish (Christ), the anchor (hope), the palm (victory), and the representation of the soul in the other world as a female figure with arms extended in prayer (orans).

Beginning with the 4th century, after the Church gained hegemony over the Empire, the language of the epitaphs became more frank and open. Emphasis was laid upon a life according to the dictates of Christian faith, and prayers for the dead were added to the inscription. The prayers inscribed thus early on the sepulchral slabs reproduce in large measure the primitive liturgy of the funeral service. They implore for the dead eternal peace and a place of refreshment (refrigerium), invite to the heavenly love-feast (Agape), and wish the departed the speedy enjoyment of the light of Paradise, and the fellowship of God and the saints.