Zostrianos is a Sethian Gnostic text. It is the first tractate of two in Codex VIII of the Nag Hammadi library. It takes up 132 of the 140 pages in the codex, making Zostrianos the longest tractate of the entire library. However the text is extensively damaged, especially in the center, making the document difficult to fully understand. The Coptic manuscript is a translation of a Greek original, likely written in Alexandria in c. 200 AD. In the text, Zostrianos goes on a heavenly journey and receives divine knowledge from the aeons.

The work is likely the same Zostrianos that Porphyry criticized in Life of Plotinus. Like other Sethian Gnostic texts Marsanes, Allogenes, and Three Steles of Seth, its ideas appear more Middle Platonic or Neoplatonic than Christian. However, Porphyry said that these works belonged to Christian heretics. Bentley Layton explains this apparent contradiction with the belief that Zostrianos was written by a Gnostic Christian author who was fascinated with Eastern religious heroes who had special knowledge relating to the divine, such as Zoroaster.

Zostrianos, writing in first person, introduces the text as eternally living words written for the living elect. He rejects material and psychic associations and searches for a place of repose for his spirit outside of the perceptible world. He experiences an initial vision of the perfect child and ponders the relationship between the ideal and phenomenal worlds, but despite diligent attempts to find answers, he is unable to do so. In his despair, he seeks a violent death in the desert but is visited by the angel of the knowledge of eternal light, who tells him that he is a chosen person and that he can be saved. The angel offers to guide Zostrianos to the world of light.

Zostrianos departs from his earthly body with a luminous cloud, which guides him through the atmospheric realm and past the aeonic copies to the self-generated aeons. He undergoes six baptisms of repentance, becoming a contemplative angel, an angel of masculine gender, a holy angel, and a perfect angel. In each of the baptisms, he stands upon a different aeon and blesses the divine Autogenes, the forefather Pigeradamas, and various other figures. Zostrianos seeks to know the single reality underlying the different levels of the cosmos and receives instructions on how to do so.

Authrounios offers to explain realms below the self-generated Aeons, including the atmospheric realm, the Aeonic Copies, and the world which does not truly exist. Zostrianos joins the aeons he has traversed. Authrounios explains the origin of the physical cosmos, stating that the atmospheric realm was created by a rational principle to manifest generated and perishable things for the sake of the advent of great judges, lest they be enclosed in the creation. When Sophia contemplated the stars, she emitted the darkness, fleeing what is subject to the Archon. The Archon saw a reflection and created the world, but the image belonging to Sophia is always corrupt and deceptive. Zostrianos responds, and the section concludes with the restoration of Sophia and the explanation of the Aeonic Copies and the illumination of souls.

The pre-existent principles are three in number and appeared from a single origin of the Barbelo aeon. These principles have manifested every principle and empowered every power, and are existence, blessedness, and life. The text then mentions the three perfect baptismal waters: water of life, water of blessedness, and water of existence. The text highlights that these waters are likenesses and forms of the Triple-Powered One, that flows from the pure water, and that they exist together with the essence and existence of being. The text further explains the generation of determinate being and how it received enlightenment and stable being through baptism. One who knows how he exists and what the living water is lives within knowledge.

The text describes the descent of various spiritual entities, which are incorporeal, undivided, and spiritually pure, but also without compulsion. Their path of ascent is pure and imperishable, and they are associated with different baptisms that lead to eternal life. Glories are appointed to guard those who are truly baptized in knowledge, and various baptisms are appointed for those who strip off the world and lay aside nature. Through knowledge and purification, one can approach unity and be filled with Holy Spirit. The text also mentions the Triple Powered Invisible Spirit and the powers of the Spirit, which can be revealed through silent thought and meditation.

The text discusses various types of souls and their level of attainment in different aeons. The first type of soul is the incarnate soul, which is divided into those that have perished and those that are within their time. There are differences among souls, but they are parts of things that endure. The second type is the disincarnate soul in the sojourn, which does not have self-generated power and follows the ways of others. The third type is the disincarnate soul in the repentance, which has three classes: those who have committed all sins and have repented, those who have partially sinned or only intended to sin. The fourth type is the self-generated ones, who have a rational expression of the ineffable truth and eternal life. The four exist as rational expressions of truth and knowledge, and they belong not to Protophanes but to the Mother. The four lights, Armazel, Oroiael, Daveithe, and Eleleth, exist as rational expressions of truth and knowledge. Furthermore, Adam is the perfect human, an eye of Autogenes, and it is his knowledge that knows the divine Autogenes.