The Shepherd of Hermas (Greek: Ποιμὴν τοῦ Ἑρμᾶ, romanized: Poimēn tou Herma; Latin: Pastor Hermae), sometimes just called The Shepherd, is a Christian literary work of the late first half of the second century, considered a valuable book by many Christians, and considered canonical scripture by some of the early Church Fathers such as Irenaeus. The Shepherd was popular among Christians in the 2nd, 3rd, and 4th centuries. It is found in the Codex Sinaiticus. The Muratorian fragment identifies the author of The Shepherd as Hermas, the brother of Pope Pius I.

The book was originally written in Rome in Koine Greek. A first Latin translation, the Vulgata (common language), was made very shortly afterwards. A second Latin translation, the Palatina, was made at the beginning of the fifth century. Of the Greek version, the last fifth or so is missing. The Vulgata is therefore the earliest translation and the most complete witness.

The Shepherd was also translated at least twice into the Coptic (Egyptian) language and fragments of translations in both the Sahidic and Akhmimic dialects survive. Three translations into Ge'ez (Ethiopic) were also made, but none survives complete. The sole surviving Georgian translation seems to have been made from an Arabic version, but no Arabic translation has been preserved. There does not appear to have been a Syriac translation and no Syriac author shows any awareness of the Shepherd. It was always more popular in the Western Roman Empire and in Alexandria than in the rest of the east. There was a Middle Persian translation made for a Manichaean readership, which survives in a single fragmentary manuscript found at Turfan in what is now China.

The book consists of five visions granted to Hermas, a former slave. This is followed by twelve mandates or commandments, and ten similitudes (aka parables). It commences abruptly in the first person: "He who brought me up sold me to a certain Rhode, who was at Rome. After many years I met her again, and began to love her as a sister." As Hermas is on the road to Cumae, he has a vision of Rhoda. She tells him that she is now his accuser in heaven, on account of unchaste and impure thoughts the (now) married narrator once had regarding her. He is to repent and pray for forgiveness, for himself and all his house. He is consoled by a vision of the Church in the form of an aged woman, weak and helpless from the sins of her unfaithful children, who tells him to bear fruits of repentance and to correct the sins of his children. Subsequently, after his repentance he sees her made younger, yet still wrinkled and with white hair; then again, later she appears as quite young but still with white hair; and lastly, she shows herself as a glorious Bride.

This allegorical language continues through the other parts of the work. In the second vision she gives Hermas a book, which she later takes back in order to add to it. The fifth vision, which is represented as taking place 20 days after the fourth, introduces "the Angel (Messenger) of repentance" in the guise of a shepherd, from whom the whole work takes its name. He delivers to Hermas a series of precepts (mandata, entolai), which form an interesting development of early Christian ethics. One point which deserves special mention is the instruction of a Christian husband's obligation to forgive and take back an adulterous wife upon her repentance. The eleventh mandate, on humility, is concerned with false prophets who desire to occupy the primary, or best seats (that is to say, among the presbyters). Some have seen here a reference to Marcion, who came to Rome c. 140 and desired to be admitted among the priests (or possibly even to become bishop of Rome).

After the mandates come ten similitudes (parabolai) in the form of visions, which are explained by the angel. The longest of these (Similitude 9) is an elaboration of the parable of the building of a tower, which had formed the matter of the third vision. The tower is the Church, and the stones of which it is built are the faithful. In the third vision it looks as though only the holy are a part of the true Church; in Similitude 9 it is clearly pointed out that all the baptized are included, though they may be cast out for grave sins, and can be readmitted only after repentance.

Textual criticism, the nature of the theology, and the author's apparent familiarity with the Book of Revelation and other Johannine texts are thought to set the date of composition in the 2nd century. However, several ancient witnesses support an early dating and there is internal evidence for the place and date of this work in the language and theology of the work. The reference to an unknown Clement is presumed by some to be Clement of Rome; if this is that Clement, it would suggest a date c. 90 for at least the historicised setting of the first two visions. Since Paul sent greetings to a Hermas, a Christian of Rome (Romans 16:14), a minority have followed Origen of Alexandria's opinion that he was the author of this religious allegory.

Three ancient witnesses claim to identify the author of this writing. These authorities may be citing the same source, perhaps Hegesippus, whose lost history of the early Church provided material for Eusebius of Caesarea. The witnesses are the Muratorian fragment, the Liberian Catalogue of Popes (a record that was later used in the writing of the Liber Pontificalis) and a poem written by "Pseudo-Tertullian" in the 3rd or 4th century AD.