Scale armour (or scale mail) is an early form of armour consisting of many individual small armour scales (plates) of various shapes attached to each other and to a backing of cloth or leather in overlapping rows. Scale armour was worn by warriors of many different cultures as well as their horses. The material used to make the scales varied and included bronze, iron, steel, rawhide, leather, cuir bouilli, seeds, horn, or pangolin scales. The variations are primarily the result of material availability.
Scale armour is armour in which the individual scales are sewn or laced to a backing by one or more edges and arranged in overlapping rows resembling the scales of a fish/reptile or roofing tiles. The scales are usually assembled and strapped by lacing or rivets. Lorica squamata is an ancient Roman armour of this type.
Other types of armour made from individual scales but constructed in a different manner have their own separate names, such as lamellar armour where the individual scales are perforated on several or all edges and lashed tightly to each other in straight ridged rows and do not need to be attached to a backing. The Romans also had a variant called lorica plumata in which the scales were attached to mail.
The Scythians' horse warriors appear to have used scale or possibly lamellar armour, evident both from contemporary illustrations and burial finds in kurgans. The armour was made from small plates of iron or bronze. Unique to the Scythians, about 20% of the females found in graves were dressed for war, some including armour, which may have inspired the Greek tales of Amazons.
Due to the semi-rigid nature of the armour, the Scythian variety was made as breast- and back-plates, with separate shoulder pieces. Some finds indicate partial armour, where a leather shirt or similar garment has sewn-on scales in places, particularly around the neck and upper chest.
The individual scales used to construct Roman armour are called squamae or squama During Roman times, scale armour (lorica squamata) was a popular alternative to mail (lorica hamata) as it offered better protection against blunt force trauma. Hellenistic-Attic lamellar armor was also widely used in Middle Eastern empires, such as Persia and Byzantium. In these areas, scales were commonly dished (that is with a bowl effect from a depression being hammered into a flat piece of metal) in order to benefit from the extra protection offered by a rounded scale.
According to the statement of Herodotus, the ancient Persians wore tunics with sleeves of diverse colours, having upon them iron scales of the shape of fish-scales; this comparison indicates scale armour, and not mail, is meant.
Scale armour is not of frequent occurrence on the grave monuments of the German frontier. On two tombstones of the Sertorii at Verona (one that of a centurion, the other that of a standard-bearer) both figures are represented wearing a tunic of scale armour which covers the shoulders and comes down below the belt. The Carnuntum monument of Calidius (a work of the middle of the first century) shows also a scaled tunic of a centurion. Again, in the collection of marble portrait-busts from the great Gallo-Roman villa of Chiragan near Toulouse, the Emperors Antoninus Pius and Severus both appear wearing corselets of scale armour.
Metal scale armour was used throughout most of the European world for the duration of the medieval period. It was commonly used to augment other armour types, predomiantly maille but also plate armour taking the form of a cuirass over mail, scale pauldorns, or fauld (the lower part of a breastplate that protects the lower stomach, hips and groin), there is also evidence for scale sabatons (protective shoe coverings)and scale aventails. The use of these scale armoured components are commonly depicted in period art and funeral effigys. The funeral effigy of Sir Albrecht Von Hohenlohe circa 1325 AD depicts him wearing scaled body armour underneath his surcoat and over a maille haubergeon, Sir Albrecht's armour appears to be additionally riveted to the backing. 
Scale armour consisting of many plates and studs were used for the military officers from the Samgukji era pre 1000BC and were very effective against light missiles such as arrows. It was also used in the battles against Japanese invasion during the 14-1500 era, which proved the armour against Japanese weapons.
Japanese (samurai) individual scales are called kozane. Japanese scale armour constructed from fish type scales (gyorin kozane) were reportedly constructed in Japan as far back as the Fujiwara period (11th century). "A primitive type of Japanese harness, the single laminae being of boiled leather, cut and beaten into pieces shaped like fish-scales."
Scale armour offers better and more solid protection from piercing and blunt attacks than maille. It is also cheaper to produce, but it is not as flexible and does not offer the same amount of coverage. Forms other than brigandine and coat of plates were uncommon in medieval Europe, but scale and lamellar remained popular elsewhere.
A similar type of modern personal armour is Dragon Skin body armour, which uses ballistic fabric and high-impact resistant ceramic plates to protect against pistol and rifle fire. However, its "scales" are not exposed.
Korean armour made of tin scale (), displayed at the Danghangpo Tourist Resort, site of the Battle of Danghangpo.
Historical re-enactment of a Sassanid-era cataphract.