Hippias of Athens (Greek: Ἱππίας ὁ Ἀθηναῖος) was one of the sons of Peisistratus, and was tyrant of Athens between about 527 BC and 510 BC when Cleomenes I of Sparta successfully invaded Athens and forced Hippias to leave Athens.
The name and family of the mother of Hippias are unknown. He succeeded Peisistratus as tyrant of Athens in 528/7 BC. His brother Hipparchus, who may have ruled jointly with him, was murdered by Harmodius and Aristogeiton (the tyrannicides) in 514 BC. Hippias executed the tyrannicides and it was said that he became a bitter and cruel ruler, executing a large number of citizens and imposing harsh taxes. Hippias's cruelty soon created unrest among his subjects. As he began losing control, he sought military support from the Persians. He managed to form an alliance by marrying his daughter, Archedike, to Aiantides, son of Hippoklos, the tyrant of Lampsakos. This relationship with Hippoklos helped facilitate Hippias' access to Darius' court at Susa.
The Alcmaeonidae family of Athens, which Peisistratus had exiled in 546 BC, was concerned about Hippias forming alliances with the Persian ruling class, and began planning an invasion to depose him. In 510 BC Cleomenes I of Sparta successfully invaded Athens and trapped Hippias on the Acropolis. They also took the Pisistratidae children hostage forcing Hippias to leave Athens in order to have them returned safely.
The Spartans later thought that a free, democratic Athens would be dangerous to Spartan power, and attempted to recall Hippias and re-establish the tyranny. Hippias had fled to Persia, and the Persians threatened to attack Athens if they did not accept Hippias back. Nevertheless, the Athenians preferred to remain democratic despite the danger from Persia.