The Periplus of the Erythraean Sea (Koinē Greek: Περίπλους τῆς Ἐρυθρᾶς Θαλάσσης, Períplous tē̂s Erythrâs Thalássēs), also known by its Latin name as the Periplus Maris Erythraei, is a Greco-Roman periplus written in Koine Greek that describes navigation and trading opportunities from Roman Egyptian ports like Berenice Troglodytica along the coast of the Red Sea and others along the Horn of Africa, the Persian Gulf, Arabian Sea and the Indian Ocean, including the modern-day Sindh region of Pakistan and southwestern regions of India.
The text has been ascribed to different dates between the first and third centuries, but a mid-first-century date is now the most commonly accepted. While the author is unknown, it is a first-hand description by someone familiar with the area and is nearly unique in providing accurate insights into what the ancient Hellenic world knew about the lands around the Indian Ocean.