Olorus (Greek: Ὄλορος) was the name of a king of Thrace. His daughter Hegesipyle married the Athenian statesman and general Miltiades, who defeated the Persians at the Battle of Marathon in 490 BC. Olorus was also the name of the father of the 5th century BC Athenian historian Thucydides, the author of the History of the Peloponnesian War.
- Herodotus. Histories, 6.39.1. "Stesagoras met his end in this way. The sons of Pisistratus sent Miltiades, son of Cimon and brother of the dead Stesagoras, in a trireme to the Chersonese to take control of the country; they had already treated him well at Athens, feigning that they had not been accessory to the death of Cimon his father, which I will relate in another place. Reaching the Chersonese, Miltiades kept himself within his house, professing thus to honor the memory of his brother Stesagoras. When the people of the Chersonese learned this, their ruling men gathered together from all the cities on every side, and came together in a group to show fellow-feeling with his mourning; but he put them in bonds. So Miltiades made himself master of the Chersonese; there he maintained a guard of five hundred men, and married Hegesipyle the daughter of Olorus, king of Thrace."
- Thucydides. History of the Peloponnesian War, 4.104.1. "The passage of Brasidas was a complete surprise to the people in the town; and the capture of many of those outside, and the flight of the rest within the wall, combined to produce great confusion among the citizens; especially as they did not trust one another. It is even said that if Brasidas, instead of stopping to pillage, had advanced straight against the town, he would probably have taken it. In fact, however, he established himself where he was and overran the country outside, and for the present remained inactive, vainly awaiting a demonstration on the part of his friends within. Meanwhile the party opposed to the traitors proved numerous enough to prevent the gates being immediately thrown open, and in concert with Eucles, the general, who had come from Athens to defend the place, sent to the other commander in Thrace, Thucydides, son of Olorus, the author of this history, who was at the isle of Thasos, a Parian colony, half a day's sail from Amphipolis, to tell him to come to their relief. On receipt of this message he at once set sail with seven ships which he had with him, in order, if possible, to reach Amphipolis in time to prevent its capitulation, or in any case to save Eion."