Megasthenes was the Greek ambassador sent by Seleucus I Nicator (the Seleucid king) to the court of Chandragupta Maurya around 305-303 BCE. He wrote 'Indica,' a valuable account of ancient Indian society, politics, and geography. Seleucus had sent him after making peace with Chandragupta following the Seleucid-Mauryan war, establishing diplomatic relations between the two empires.