The Periplus of the Erythraean Sea (Periplus Maris Erythraei) is a Greek periplus, describing navigation and trading opportunities from Roman Egyptian ports like Berenice along the coast of the Red Sea, and others along East Africa and India. The text has been ascribed to different dates between the 1st and 3rd century CE, but a mid first century date is now the most commonly accepted. Although the author is unknown, it is clearly a firsthand description by someone familiar with the area, and is nearly unique in providing accurate insights into what the ancient world knew about the lands around the Indian Ocean.

Although the "Erythraean Sea" is generally held to be the ancient term for the Red Sea, to the Greeks it included the Indian Ocean and the Persian Gulf.

The work consists of 66 chapters, most of them about the length of a long paragraph in English. For instance, the short Chapter 9 reads in its entirety:

"From Malao (Berbera) it is two courses to the mart of Moundou, where ships anchor more safely by an island lying very close to the land. The imports to this are as aforesaid [Chapter 8 mentions iron, gold, silver, drinking cups, etc], and from it likewise are exported the same goods [Chapter 8 mentions myrrh, douaka, makeir, and slaves], and fragrant gum called mokrotou. The inhabitants who trade here are more stubborn." In many cases the description of places is sufficiently accurate to identify their present locations; for others there is considerable debate. For instance, a "Rhapta" is mentioned as the farthest market down the African coast of "Azania", but there at least five locations matching the description, ranging from Tanga south to the Rufiji River delta. The description of the Indian coast mentions the Ganges River clearly, yet after that is somewhat garbled, describing China as a "great inland city Thina" that is a source of raw silk.

Another interesting feature of the Periplus is that some of the words describing trade goods are seen nowhere else in ancient literature, and so we can only guess as to what they might mean. The Periplus also describes how Hippalus first discovered the direct route from the Red Sea to southern India.

The text derives from a Byzantine 10th century manuscript in minuscule hand, contained in the collections of the University Library of Heidelberg (CPG 398: 40v-54v) and a copy of it dating from the 14th or 15th century in the British Museum. In the 10th century manuscript the text is attributed to Arrian, probably for no deeper reason than that the manuscript was adjacent to the Periplus Pontus Euxini written by him. The Periplus was first published in a modern edition by Sigismund Gelenius in 1553.