A cataphract was a form of armoured heavy cavalry that originated in Persia and was fielded in ancient warfare throughout Eurasia and Northern Africa.

Historically, the cataphract was a very heavily armoured horseman, with both the rider and mount almost completely covered in scale or lamellar armour over chain mail, and typically wielding a kontos (lance) as his primary weapon.

Cataphracts served as the elite cavalry force for most empires and nations that fielded them, primarily used for charges to break through opposing heavy cavalry and infantry formations. Chronicled by many historians from the earliest days of antiquity up until the High Middle Ages, they may have influenced the later European knights, through contact with the Eastern Roman Empire.

Peoples and states deploying cataphracts at some point in their history included: the Scythians, Sarmatians, Alans, Medes, Parthians, Achaemenids, Sakas, Indians, Armenians, Seleucids, Attalid, Pontus, Greco-Bactrian, Sassanids, Romans, Goths, Byzantines, Georgians, Chinese, Koreans, Jurchens, Mongols, Tanguts and Songhai.

In Europe, the fashion for heavily armoured Roman cavalry seems to have been a response to the Eastern campaigns of the Parthians and Sasanians in Anatolia, as well as numerous defeats at the hands of Iranian cataphracts across the steppes of Eurasia, most notably in the Battle of Carrhae (53 BC) in upper Mesopotamia. Traditionally, Roman cavalry was neither heavily-armoured nor decisive in effect; the Roman equites corps comprised mainly lightly-armoured horsemen bearing spears and swords and using light cavalry tactics to skirmish before and during battles, and then to pursue retreating enemies after a victory. The adoption of cataphract-like cavalry formations took hold among the late Roman army during the late 3rd and 4th centuries. The Emperor Gallienus (r. 253–268 AD) and his general and putative usurper Aureolus (died 268) arguably contributed much to the institution of Roman cataphract contingents in the Late Roman army.

The origin of the word is Greek. Κατάφρακτος (kataphraktos, cataphraktos, cataphractos, or katafraktos) is composed of the Greek root words, κατά, a preposition, and φρακτός ("covered, protected"), which is interpreted along the lines of "fully armoured" or "closed from all sides". The term first appears substantively in Latin, in the writings of Lucius Cornelius Sisenna: "loricatos, quos cataphractos vocant", meaning "the armoured, whom they call cataphract".

There appears to be some confusion about the term in the late Roman period, as armoured cavalrymen of any sort that were traditionally referred to as Equites in the Republican period later became exclusively designated as "cataphracts". Vegetius, writing in the fourth century, described armour of any sort as "cataphracts" – which at the time of writing would have been either lorica segmentata or lorica hamata. Ammianus Marcellinus, Roman soldier and historian of the fourth century, mentions the "cataphracti equites (quos clibanarios dictitant)" – the "cataphract cavalry which they regularly call clibanarii" (implying that clibanarii is a foreign term, not used in Classical Latin).

Clibanarii is a Latin word for "mail-clad riders", itself a derivative of the Greek κλιβανοφόροι (klibanophoroi), meaning "camp oven bearers" from the Greek word κλίβανος, meaning "camp oven" or "metallic furnace"; the word has also been tentatively linked to the Persian word for a warrior, grivpan. However, it appears with more frequency in Latin sources than in Greek throughout antiquity. A twofold origin of the Greek term has been proposed: either that it was a humorous reference to the heavily armoured cataphracts as men encased in armour who would heat up very quickly much like in an oven; or that it was further derived from the Old Persian word *griwbanar (or *grivpanvar), itself composed of the Iranian roots griva-pana-bara, which translates into "neck-guard wearer".