A periplus (//) is a manuscript document listing, in order, the ports and coastal landmarks, with approximate intervening distances, that the captain of a vessel could expect to find along a shore. It served the same purpose as the later Roman itinerarium of road stops; however, the Greek navigators added various notes, which if they were professional geographers (as many were) became part of their own additions to Greek geography. In that sense the periplus was a type of log.
The form of the periplus is at least as old as the earliest Greek historian, the Ionian Hecataeus of Miletus. The works of Herodotus and Thucydides contain passages that appear to have been based on peripli.
Periplus is the Latinization of the Greek word περίπλους (periplous, contracted from περίπλοος periploos), literally "a sailing-around." Both segments, peri- and -plous, were independently productive: the ancient Greek speaker understood the word in its literal sense; however, it developed a few specialized meanings, one of which became a standard term in the ancient navigation of Phoenicians, Greeks, and Romans.
In the Persian Gulf
These Rahnamehs listed the ports and coastal landmarks and distances along the shores.
These lost but much-cited sailing directions go back at least until the twelfth century. In Rahnamehs, the Indian Ocean was described as "a hard sea to get out of" and warned of the "circumambient sea, whence all return was impossible.
Several examples of peripli have survived:
- The Periplus of Hanno the Navigator, a 6th-century BCE Carthaginian colonist and explorer, described the coast of Africa from present-day Morocco deep into the Gulf of Guinea.
- The Massaliote Periplus, a description of trade routes along the coasts of Atlantic Europe, possibly dating to the 6th century BCE
- Pytheas of Massilia, (4th century BCE) On the Ocean (Περί του Ωκεανού), has not survived; only excerpts remain, quoted or paraphrased by later authors, notably in Avienus' Ora maritima.
- The Periplus of Pseudo-Scylax, generally thought to date to the 4th or 3rd century BCE.
- The Periplus of the Erythraean Sea was written by a Romanized Alexandrian in the 1st century CE. It gives the shoreline itinerary of the Red (Erythraean) Sea, starting each time at the port of Berenice. Beyond the Red Sea, the manuscript describes the coast of India as far as the Ganges River and the east coast of Africa (called Azania). The unknown author of the Periplus of the Red Sea claims that Hippalus, a mariner, was knowledgable about the "monsoon winds" that shorten the round-trip from India to the Red Sea.  According to the Periplus of the Red Sea, "the Horn of Africa," was called, "the Cape of Spices."  The author of the text Periplus of the Red Sea called modern day Yemen the "Frankincense Country." 
- The Periplus Ponti Euxini, a description of trade routes along the coasts of the Black Sea, written by Arrian in the early 2nd century CE.
A periplus was also an ancient naval manoeuvre in which attacking triremes would outflank or encircle the defenders in order to attack them in the rear.
- Kish, George (1978). A Source Book in Geography. Cambridge: Harvard University Press. p. 21. ISBN 978-0-674-82270-2.
- Shahar, Yuval (2004). Josephus Geographicus: The Classical Context of Geography in Josephus. Mohr Siebeck. p. 40. ISBN 978-3-16-148256-4.
- Dehkhoda, Ali Akbar, and Mohammad Moʻin. 1958. Loghat-namehʻi Dehkhoda. Tehran: Tehran University Press: Rahnāma.
- Civilizations: Culture, Ambition, and the Transformation of Nature - culture, ambition, and the transformation of nature. By Felipe Fernandez-Armesto. Free Press (2001)
- Xinru Liu, The Silk Road in World History (New York: Oxford University Press, 2010), 34.
- Xinru Liu, The Silk Road in World History (New York: Oxford University Press, 2010), 36.
- Xinru Liu, The Silk Road in World History (New York: Oxford University Press, 2010), 37.
- The dictionary definition of periplus at Wiktionary