Actaeus belongs to the legendary ancestry of Attica, a landscape whose early rulers were often imagined as autochthons, people born from the earth itself. Such figures held a special place in Athenian imagination because they expressed a claim of enduring belonging: the ancestors had not arrived from foreign shores but were inseparable from the land. This was a story about identity, not historical proof that a king had risen from the soil. His very name, Aktaîos, meant coast-man or shore-dweller, and the land he ruled bore that name in turn: Acte, or Actica, the coastal kingdom that stretched along the Aegean shore before any city walls were raised. Some later writers, looking back across the centuries, named a different man as the first ruler: Colaenus, a figure remembered only by the people of Myrrhinos, a parish of Attica. Pausanias, the Greek traveller of the second century CE, records Actaeus as the first ruler in the main Athenian succession while also preserving differing local traditions.

He ruled in the age before memory, before the mythical Flood of Deucalion, the survivor of a great deluge in Greek tradition. In that dim time, before writing and before stone temples, Actaeus governed the coastal settlements of Attica from a throne that left no ruins and issued laws that left no inscriptions. The surviving accounts tell us very little about his reign beyond its place near the beginning of the legendary succession. He was not a warrior-king like Agamemnon, not a lawgiver like Solon, not a builder like Pericles. He was simply the first, and in a culture that valued antiquity above almost every other virtue, that was enough.

What survives of Actaeus survives through his daughters. He had at least one, and perhaps four. The daughter named in the principal genealogy was Aglaurus, also called Agraulus, who married Cecrops, the autochthonous king whose body was half man and half serpent. Cecrops inherited the throne of Acte through this marriage, and when he took power he renamed the land Cecropia after himself, the first of many names the peninsula would wear before it became Attica. Through Aglaurus, Actaeus became the grandfather of Erysichthon, who died before his father and left no heir, and of three granddaughters who would shape the destiny of Athens: Aglaurus the younger, Herse, and Pandrosos. It was these three girls who, according to the most famous version of the myth, were given a chest by Athena containing the infant Erichthonius, the earth-born child of Hephaestus and Gaia, and who were forbidden to open it. Their curiosity cost two of them their lives, and from that chest emerged a line of kings remembered in the legendary ancestry of Athens.

Some sources give Actaeus three more daughters beyond Aglaurus: Herse, Pandrosos, and a fourth named Phoenice, who died without ever marrying. The Byzantine Suda, under its entry for Phoenician letters, preserves a curious claim attributed to Scamon of Mytilene: a king's daughter Phoenice was commemorated in their name. This account is associated with Actaeus, although the transmitted name and family relationships differ from the main genealogy. Whether this is historical fancy or a genuine tradition lost to time, it places Actaeus at the very edge of the known and the guessed, a king whose family was so ancient that even the alphabet was said to remember them. Apollodorus, in the handbook known as the Library, calls Cecrops the first king of Attica but still identifies his wife Aglaurus as the daughter of Actaeus. The three famous girls belong to Cecrops and Aglaurus together in this genealogy. The difference concerns the starting point of the royal succession; it does not mean that the girls were not their mother's daughters. The deeper past remains a place of overlapping traditions rather than a single agreed family history.

Actaeus left no monuments, no laws, and no wars. His kingdom vanished into the name of his successor, and his people became the Cecropidae, the sons of Cecrops. Yet his name survived in the Parian Chronicle, the marble record of ancient history inscribed on the island of Paros, which recalled Actaeus in its explanation of Attica's earlier name while beginning its dated account with Cecrops. And it survived in Pausanias, who walked the streets of Athens and remembered that before Cecropia, before Athens, before Athena and Poseidon ever fought for the rock, there was a man named Actaeus who stood on the coast and called the shore his own.