In Greek mythology, ichor (/ˈaɪkər/) is the ethereal fluid making up the blood of the gods and/or immortals. The Ancient Greek word ἰχώρ (ikhṓr) is of uncertain etymology, and has been suggested to be a foreign word, possibly the pre-Greek substrate.

Ichor originates in Greek mythology, where it is the "ethereal fluid" that is the blood of the Greek gods, sometimes said to retain the qualities of the immortals' food and drink, ambrosia and nectar. Ichor is described as toxic to humans, killing them instantly if they came in contact with it. Great heroes and demigods occasionally attacked gods and released ichor, but gods rarely did so to each other in Homeric myth.^{[original research?]}

According to G.S. Kirk, the term is used in the sense of "divine equivalent of blood" only twice, in the Homeric passages of the Iliad. The goddess Athena confers on Diomedes the ability to distinguish gods and mortals, and grants specific permission to wound Aphrodite.:

πρυμνὸν ὕπερ θέναρος· ῥέε δ᾽ ἄμβροτον αἷμα θεοῖο  
ἰχώρ, οἷός πέρ τε ῥέει μακάρεσσι θεοῖσιν·
οὐ γὰρ σῖτον ἔδουσ᾽, οὐ πίνουσ᾽ αἴθοπα οἶνον,
τοὔνεκ᾽ ἀναίμονές εἰσι καὶ ἀθάνατοι καλέονται·

[His spear.. struck Aphrodite at the base of her palm,] Blood [flowed], but immortal [blood at that]: ichor pure,
Such as the blessed inhabitants of heaven may bleed,
For the Gods eat not man's food,
Nor [drink sparkling] wine,
For they are bloodless and [called] death-exempt [Athanatoi, or "Immortals"].

The scene where Diomedes with spear is on the verge of confronting and wounding Aphrodite is depicted on the Sarti tabula iliaca (cf. fig. right).

In the second passage shortly after in the Iliad where ichor recurs, Aphrodite (Dione) merely wipes the ichor (ἰχῶ, v. 416) with both her hands, and she is none the worse for wear. So despite the agony it carried, the wound inflicted by the mortal turned out to be but a slight one.

In Ancient Crete, tradition told of Talos, a giant man of bronze and ichor. Apollodotus explains that Talos had a single vein running from neck to ankle, pinned down by bronze nails. Talos encircled the island, guarding it, so that when the Argonauts arrived (having already acquired the Golden Fleece), Talos threw boulders at their ship. The sorceress Medea defeated it by either driving it to madness with drugs, or falsely promising to give it immortality, and pulling out the nail (presumably the lower one at the ankle) draining out all its ichor. In Apollonius of Rhodes's account, Talos nicked its ankle on a crag and the precious ichor gushed out like molten lead.