The dory or doru (/ˈdɒruː/; Greek: δόρυ) was the chief spear of hoplites (heavy infantry) in Ancient Greece. A small dory was called doration (δοράτιον). The word doru is first attested in the Homeric epics with the meanings of "wood" and "spear". Homeric heroes hold two dorata (Greek: δόρατα, plural of δόρυ) (Il. 11,43, Od. 1, 256).

The spear used by the Persian army under Darius I and Xerxes in their respective campaigns during the Greco-Persian Wars was shorter than that of their Greek opponents. The dory's length enabled multiple ranks of a formation to engage simultaneously during combat.

The dory was not intended for throwing, such as a dart or javelin. However, its aerodynamic shape allowed the dory to be thrown. Because it had evolved for combat between phalanxes, it was constructed so as to be adequate against the defences of Greek infantry, which incorporated bronze in shield and helmet construction. Hoplites were generally more heavily armored than infantry of their non-Greek contemporaries.

Should not be confused with Dorydrepanon (δορυδρέπανον, from δόρυ (Dory) + δρέπανον (Sickle)) which was a kind of Halberd and was used for cutting off halyards in sea-fights and for pulling down battlements in sieges.

In classical antiquity, the dory was a symbol of military power, possibly more important than the sword, as can be inferred from expressions like "Troy conquered by dory" (Il. 16,708) and words like "doryktetos" (Greek: δορίκτητος) (spear-won) and "doryalotos" (Greek: δορυάλωτος) (spear-taken). Doriklutos (Δορίκλυτος) means "spear-famed" or "renowned for the spear", while the expression "dorikthtos ploutos" (δορίκτητος πλοῦτος, "spear-won wealth") refers to wealth gained through war.

The Greeks also used the expression "Σὺν δορί, σὺν ἀσπίδι" ("with spear (dory) and shield") as a proverb meaning "to pursue something by every possible means".

Dory kerykeion (Δόρυ κηρύκειον; "A spear as a herald's wand") was a Greek proverb used of people who both urge or reassure and threaten at the same time, presenting themselves as peaceful while preparing for violence. It comes from a story in which the Gephyraeans, after consulting the oracle at Delphi, migrated to Tanagra during a war involving Athens and Eumolpus, sending a leader ahead with a herald's staff as a sign of peace while armed men followed behind.

The dory was about 2–3 meters in length (6'7" in. to 9'10” in.) and had a handle with a diameter of 5 cm (2 in) made of wood, either cornel or ash weighing 0.91 to 1.81 kg (2.0 to 4.0 lb). The flat leaf-shaped spearhead was made of iron and its weight was counterbalanced by an iron butt-spike. (cf Sarissa)