Erichthonius (Ancient Greek: Ἐριχθόνιος) was a king of Troy in Greek mythology. He was the son of Dardanus and Batea (in some legends his mother is Olizone, daughter of Phineus). He was the brother of Ilus and Zacynthus. His wife was Astyoche, daughter of the river-god Simoeis, by whom he became father of Tros.

Erichthonius is of uncertain etymology, possibly related to a pre-Greek form *Erekteu-. The connection of Ἐριχθόνιος with ἐρέχθω, "shake" is a late folk-etymology; other folk-etymologies include ἔριον, erion, "wool" or eris, "strife"+ χθών chthôn or chthonos, "earth".

Fundamentally, all that is known of this Erichthonius comes from Homer, who says (Samuel Butler's translation of Iliad 20.215-234):

John Tzetzes and one of the scholia to Lycophron call his wife Astyoche, the naiad daughter of the river-god Simoeis. The Bibliotheca also adds Erichthonius' older brother Ilus, who died young and childless; presumably a doublet of the other Ilus, grandson of Erichthonius, eponym of Troy. In one account, Erichthonius was said to be the father of Ganymede.

Strabo records, but discounts, the claim by "some more recent writers" that Teucer came from the deme of Xypeteones in Attica, supposedly called Troes (meaning Trojans) in mythical times. These writers mentioned that Erichthonius appears as founder both in Attica and the Troad, and may be identifying the two.

Erichthonius reigned for forty six or, according to others, sixty five years and was succeeded by his son Tros.

This atlas entry (erichthonius-troy) is the Dardanian king, son of Dardanus and father of Tros. The Athenian earthborn king Erichthonius is tracked as erichthonius-athens.