Megasthenes (350 BC - c. 290 BC) was an ancient Greek historian, diplomat and Indian ethnographer and explorer in the Hellenistic period. He described India in his book Indika, which is now lost, but has been partially reconstructed from the writings of the later authors. While Megasthenes's account of India has survived in the later works, little is known about him as a person, except that he was a Greek man. He must have been a learned man, as evident by the book he wrote. His appointment as an ambassador to India suggests that he must have been a reputed officer by this time.
At the time of treaty between the Greek ruler Seleucus I Nicator and the Indian ruler Chandragupta Maurya in c. 303 BC, he appears to have been serving as an officer under Sibyrtius, who was Seleucus's satrap of Arachosia. According to Arrian, Megasthenes lived in Arachosia and travelled to Pataliputra. Megasthenes also visited the Maurya capital Pataliputra, but it is not certain which other parts of India he visited. He appears to have passed through the Punjab region in north-western India, as he provides a detailed account of the rivers in this area. He must have then traveled to Pataliputra along the Yamuna and the Ganga rivers. Megasthenes compiled information about India in form of Indika, which is now a lost work, but survives in form of quotations by the later writers.
Among the ancient writers, Arrian (2nd century AD) is the only one who speaks favorably of Megasthenes. Diodorus (1st century BC) quotes Megasthenes by omitting some parts of his narratives. Other writers explicitly criticize Megasthenes: Eratosthenes (2nd century BCE) accuses Megasthenes of engaging in falsehood, although he apparently borrowed much of his content about India from Megasthenes. Strabo (1st century AD) calls Megasthenes a liar for writing fabulous stories about India; he also brands as liars the other earlier writers on India, including Deimachus, Onesicritus, Nearchus. According to Strabo, "no faith whatever can be placed in Deimachos and Megasthenes". Pliny (1st century AD) criticizes Megasthenes's description of the races of India, and his account of Herakles and Dionysus.
Modern scholars such as E. A. Schwanbeck, B. C. J. Timmer, and Truesdell Sparhawk Brown, have characterized Megasthenes as a generally reliable source of Indian history. Schwanbeck finds faults only with Megasthenes's description of the gods worshipped in India. Brown is more critical of Megasthenes, but notes that Megasthenes visited only a small part of India, and must have relied on others for his observations: some of these observations seem to be erroneous, but others cannot be ignored by modern researchers. Thus, although he was often misled by the erroneous information provided by others, much of the information provided by him appears to be accurate, as evident by the fact that his work remained the principal source of information about India to the subsequent writers.
Thomas C. Mcevilley (2012). The Shape of Ancient Thought: Comparative Studies in Greek and Indian Philosophies. Allworth. p. 538. ISBN 978-1-58115-933-2. Three Greek ambassadors are known by name: Megasthenes, ambassador to Chandragupta; Deimachus, ambassador to Chandragupta's son Bindusara; and Dyonisius, whom Ptolemy Philadelphus sent to the court of Ashoka, Bindusara's son