Histiaeus (died 494 BC), the son of Lysagoras, was the tyrant of Miletus in the late 6th century BC.

Histiaeus owed his status as tyrant to Darius I, king of Persia, who had subjugated Miletus and the other Ionian states in Asia Minor. According to Herodotus, Histiaeus, along with the other tyrants under Darius' rule, accompanied the Persian expedition against the Scythians, and were put in charge of the defense of Darius' bridge across the Danube. The Scythians attempted to persuade Histiaeus and the others to abandon the bridge; one faction, led by Miltiades of Athens, at that time tyrant of the Chersonese, wanted to follow the Scythians' advice, but Histiaeus argued that they should stay, as they owed their power to Darius and would surely lose it if he were killed. Histiaeus suggested that they pretend to follow the Scythian plan, and was sent sent as an ambassador to tell them this, while the rest of the tyrants pretended to demolish the bridge. He told the Scythians to go look for the now-supposedly abandoned Persians, and when the Persians returned to the Danube while the Scythians were away, Histiaeus organized the ships to ferry them across.

During the expedition Histiaeus had started building a settlement at Myrcinus (site of the later Amphipolis) on the Strymon river. After returning to Sardis with Darius, Darius asked him what he wanted in return for his service, and Histiaeus responded that he wanted Myrcinus, which he was at first awarded. The Persian commander Megabazus suspected Histiaeus' interest in the strategically important area, which controlled the roads into Europe, as well as many sources of silver and timber. Darius did not believe Histiaeus was disloyal, but asked him to come back to Susa with him as a friend and advisor. Histiaeus' nephew and son-in-law Aristagoras was left in control of Miletus.

Histiaeus did not like living in Susa, and made plans to restore his power in Miletus by instigating a revolt in Ionia. In 499 BC, he shaved the head of his most trusted slave, tattooed a message on his head, and then waited for his hair to grow back. The slave was then sent to Aristagoras, who was instructed to shave the slave's head again and read the message, which told him to revolt against the Persians. Aristagoras, who was disliked by his own subjects after an expedition to Naxos ended in failure, followed Histiaeus' command, and with help from the Athenians, attacked and burned Sardis. According to Herodotus this was the entire cause of the revolt, although this is very unlikely. When Darius learned of the revolt, he sent for Histiaeus, who pretended to have no knowledge of its origins, but asked to be sent back to put it down. Darius was fooled and permitted him to leave.

On his way back, Histiaeus went to Sardis, where the satrap Artaphernes also asked him what was the cause of the revolt. Histiaeus again pretended to have no idea, but Artaphernes knew the whole story. Histiaeus was forced to flee to Chios, but attempted to implicate some of the other Persians in Sardis, who were then killed by Artaphernes. Histiaeus tried to build a fleet on Chios, but was unsuccessful, and instead tried to restore himself as tyrant of Miletus. The Miletians did not want a return to tyranny and exiled him to Lesbos. There, he gathered some ships and, according to Herodotus, began committing acts of piracy in the Black Sea and the Aegean Sea from a base in Byzantium. It is also possible that Darius had simply given him control of the Bosporus during the revolt.

Meanwhile, the Persians put down the revolt at the Battle of Lade in 494. When Histiaeus learned of this he left Byzantium, attacked Chios, and blockaded Thasos, and then attempted to land on the mainland to attack the Persians. After joining a Greek force in battle against the Persians, he was captured by the Persian general Harpagus. The satrap Artaphernes did not want to send him back to Susa, where he knew Darius would pardon him, so he executed him and sent his mummified head to Darius. Darius still did not believe Histiaeus was a traitor and gave his head an honourable burial.

Other Milesians