The kopis is an ancient single-edged sword with a heavy forward-curving blade, designed for delivering strong cleaving blows. Some scholars feel this was developed from the Cannan/Egyptian khopesh. In turn, it is often compared to the shorter Nepalese kukri and the Iberian falcata and may be their predecessor. The word itself is the Greek feminine singular noun derived from the verb κόπτω (kopt?), meaning "to cut." The difference in meaning between kopis and makhaira (another Greek word of similar meaning) is not entirely clear in ancient texts, but modern specialists tend to use both terms referred to a class of curved weapons, the only real difference being the direction of the blade curvature.

Though kopis is a Greek word, the ancient Greeks did not often use curved blades in warfare, preferring rather the straight, more martially versatile xiphos.

Greek art shows Persian soldiers wielding the kopis or an axe rather than the straight-bladed Persian akinakes.