Heraldry (also known as armory) is a discipline relating to the design, display, study and transmission of armorial bearings. A full heraldic achievement may include a coat of arms on a shield, helmet and crest, together with accompanying devices, such as supporters, badges, heraldic banners and mottoes. Heraldic achievements are formally described in a blazon.

Although the use of various devices to signify individuals and groups goes back to antiquity, both the form and use of such devices varied widely, as the concept of regular, hereditary designs, constituting the distinguishing feature of heraldry, did not develop until the High Middle Ages. It is often claimed that the use of helmets with face guards during this period made it difficult to recognize one's commanders in the field when large armies gathered together for extended periods, necessitating the development of heraldry as a symbolic language, but there is little support for this view.

The perceived beauty and pageantry of heraldic designs allowed them to survive the gradual abandonment of armour on the battlefield during the seventeenth century. Heraldry has been described poetically as "the handmaid of history", "the shorthand of history", and "the floral border in the garden of history". In modern times, individuals, public and private organizations, corporations, cities, towns, regions, and other entities use heraldry and its conventions to symbolize their heritage, achievements, and aspirations.

Related disciplines include vexillology (the study of flags), genealogy, and the studies of ceremony and rank.

Various symbols have been used to represent individuals or groups for thousands of years. The earliest representations of distinct persons and regions in Egyptian art show the use of standards topped with the images or symbols of various gods, and the names of kings appear upon emblems known as serekhs, representing the king's palace, and usually topped with a falcon representing the god Horus, of whom the king was regarded as the earthly incarnation. Similar emblems and devices are found in ancient Mesopotamian art of the same period, and the precursors of heraldic beasts such as the griffin can also be found. In the Bible, the Book of Numbers refers to the standards and ensigns of the children of Israel, who were commanded to gather beneath these emblems and declare their pedigrees. The Greek and Latin writers frequently describe the shields and symbols of various heroes, and units of the Roman army were sometimes identified by distinctive markings on their shields. At least one pre-historic European object, the Nebra sky disc, is also thought to serve as a heraldic precursor.

Until the nineteenth century, it was common for heraldic writers to cite examples such as these, and metaphorical symbols such as the "Lion of Judah" or "Eagle of the Caesars", as evidence of the antiquity of heraldry itself; and to infer that the great figures of ancient history bore arms representing their noble status and descent. The Book of Saint Albans, compiled in 1486, declares that Christ himself was a gentleman of coat armour. These claims are now regarded as the fantasy of medieval heralds, as there is no evidence of a distinctive symbolic language akin to that of heraldry during this early period; nor do many of the shields described in antiquity bear a close resemblance to those of medieval heraldry; nor is there any evidence that specific symbols or designs were passed down from one generation to the next, representing a particular person or line of descent.

The medieval heralds also devised arms for various knights and lords from history and literature. Notable examples are the toads attributed to Pharamond, the cross and martlets of Edward the Confessor, and the various arms attributed to the Nine Worthies and the Knights of the Round Table. These too are readily dismissed as fanciful inventions, rather than evidence of the antiquity of heraldry.

The development of the modern heraldic language cannot be attributed to a single individual, time, or place. Although certain designs that are now considered heraldic were evidently in use during the eleventh century, most accounts and depictions of shields up to the beginning of the twelfth century contain little or no evidence of their heraldic character. For example, the Bayeux Tapestry, illustrating the Norman invasion of England in 1066, and probably commissioned about 1077, when the cathedral of Bayeux was rebuilt, depicts a number of shields of various shapes and designs, many of which are plain, while others are decorated with dragons, crosses, or other typically heraldic figures. Yet no individual is depicted twice bearing the same arms, nor are any of the descendants of the various persons depicted known to have borne devices resembling those in the tapestry.