The Gospel of Truth is one of the Gnostic texts from the New Testament apocrypha found in the Nag Hammadi codices ("NHC"). It exists in two Coptic translations, a Subakhmimic rendition surviving almost in full in the first codex (the "Jung Codex") and a Sahidic in fragments in the twelfth.
The Gospel of Truth was probably written in Greek between 140 and 180 by Valentinian Gnostics (or, as some posit, by Valentinus himself). It was known to Irenaeus of Lyons, who objected to its Gnostic content and declared it heresy. Irenaeus declares it one of the works of the disciples of "Valentinius", and the similarity of the work to others thought to be by Valentinus and his followers has made many scholars agree with Irenaeus on this point.
But the followers of Valentinus, putting away all fear, bring forward their own compositions and boast that they have more Gospels than really exist. Indeed their audacity has gone so far that they entitle their recent composition the Gospel of Truth, though it agrees in nothing with the Gospels of the apostles, and so no Gospel of theirs is free from blasphemy. For if what they produce is the Gospel of Truth, and is different from those the apostles handed down to us, those who care to can learn how it can be show from the Scriptures themselves that [then] what is handed down from the apostles is not the Gospel of Truth.
After its Coptic translations and their burial at Nag Hammadi, the text had been lost until the Nag Hammadi discovery.
The text is written with strong poetic skill (notable even in translation), and includes a heavily cyclical presentation of themes. It is not a "gospel" in the sense of an account of the works of Jesus of Nazareth, but is better understood as a homily. The text is generally considered by scholars one of the best written texts in the whole Nag Hammadi collection, considering its worth highly as both a great literary work and a gnostic exegesis on several gospels, canonical and otherwise.