The Doric order is one of the three orders of ancient Greek and later Roman architecture; the other two canonical orders were the Ionic and the Corinthian. The Doric is most easily recognized by the simple circular capitals at the top of the columns. Originating in the western Doric region of Greece, it is the earliest and, in its essence, the simplest of the orders, though still with complex details in the entablature above.

The Greek Doric column was fluted, and had no base, dropping straight into the stylobate or platform on which the temple or other building stood. The capital was a simple circular form, with some mouldings, under a square cushion that is very wide in early versions, but later more restrained. Above a plain architrave, the complexity comes in the frieze, where the two features originally unique to the Doric, the triglyph and gutta, are skeuomorphic memories of the beams and retaining pegs of the wooden constructions that preceded stone Doric temples. In stone they are purely ornamental.

The relatively uncommon Roman and Renaissance Doric retained these, and often introduced thin layers of moulding or further ornament, as well as often using plain columns. More often they used versions of the Tuscan order, elaborated for nationalistic reasons by Italian Renaissance writers, which is in effect a simplified Doric, with un-fluted columns and a simpler entablature with no triglyphs or guttae. The Doric order was much used in Greek Revival architecture from the 18th century onwards; often earlier Greek versions were used, with wider columns and no bases to them.

The ancient architect and architectural historian Vitruvius associates the Doric with masculine proportions (the Ionic representing the feminine). It is also normally the cheapest of the orders to use. When the three orders are superposed, it is usual for the Doric to be at the bottom, with the Ionic and then the Corinthian above, and the Doric, as "strongest", is often used on the ground floor below another order in the storey above.

In their original Greek version, Doric columns stood directly on the flat pavement (the stylobate) of a temple without a base. With a height only four to eight times their diameter, the columns were the most squat of all the classical orders; their vertical shafts were fluted with 20 parallel concave grooves, each rising to a sharp edge called an arris. They were topped by a smooth capital that flared from the column to meet a square abacus at the intersection with the horizontal beam (architrave) that they carried.

The Parthenon is in the Doric order, and in antiquity and subsequently has been recognized as the most perfect example of the evolved order. It was most popular in the Archaic Period (750–480 BC) in mainland Greece, and also found in Magna Graecia (southern Italy), as in the three temples at Paestum. These are in Archaic Doric, where the capitals spread wide from the column compared to later Classical forms, as exemplified in the Parthenon.

Pronounced features of both Greek and Roman versions of the Doric order are the alternating triglyphs and metopes. The triglyphs are decoratively grooved with two vertical grooves ("tri-glyph") and represent the original wooden end-beams, which rest on the plain architrave that occupies the lower half of the entablature. Under each triglyph are peglike "stagons" or "guttae" (literally: drops) that appear as if they were hammered in from below to stabilize the post-and-beam (trabeated) construction. They also served to "organize" rainwater runoff from above. The spaces between the triglyphs are the "metopes". They may be left plain, or they may be carved in low relief.

The spacing of the triglyphs caused problems which took some time to resolve. A triglyph is centered above every column, with another (or sometimes two) between columns, though the Greeks felt that the corner triglyph should form the corner of the entablature, creating an inharmonious mismatch with the supporting column.