The first instance of a figure of the lion as symbol of the Kingdom of León is found in minted coins of Alfonso VII, called the Emperor (1126–1157). Until then, the cross had a preponderant position on documents and coins of Leonese monarchs since that reign the cross was gradually displaced by the lion. The Spanish historian and heraldist Martín de Riquer explained that the lion was already used as heraldic emblem in 1148. At the end of the reign of Alfonso VII, the figure of this animal began to appear on royal documents as personal device of the monarch and became pervasive during reigns of Ferdinand II (1157-1188) and Alfonso IX (1188-1230).
The first reference to the lion as personal emblem of the monarch, and thus the kingdom find in Chronica Adefonsi imperatoris, at the times of Alfonso VII, this chronicle when describing participants armies in the taking of Almería, the text literally says:
The heraldic symbol of León is the prominent feature of flags of León, including the historical standards of the former Kingdom of León, the flags of the City of León and the Province of León, and others representing the region known as León or the Leonese Country.
History
One of the earliest heraldic symbols in Europe
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.
The animals of the "barbarian" (Eurasian) predecessors of heraldic designs are likely to have been used as clan symbols. Adopted in Germanic tradition around the fifth century, they were re-interpreted in a Christian context in the western kingdoms of Gaul and Italy in the 6th and seventh centuries.
During the eleventh century, crosses appearing on seals of Spanish princes and were used for authentication privileges until King Alfonso VII started using a lion (1126), alluding to the name of his main realm lion (), an example of canting arms.
The lion as a heraldic charge is present from the very earliest development of heraldry in the 12th century. One of the earliest known examples of armory as it subsequently came to be practiced decorates the tomb of Geoffrey Plantagenet, Count of Anjou, who died in 1151. An enamel, probably commissioned by Geoffrey's widow between 1155 and 1160, depicts him carrying a blue shield with golden lions rampant and wearing a blue helmet adorned with another lion. A chronicle dated to about 1175 states that Geoffrey was given a badge of a gold lion when he was knighted by his father-in-law, Henry I, in 1128.
Alfonso VII's use of the lion as a heraldic emblem for León predates the earliest surviving Royal Arms of England, a single lion visible on a half-shield depicted on the First Great Seal (1189) of Richard I, as well as the three pale blue lions passant of Denmark (ca. 1194), the heraldry of the Holy Roman Empire (ca. 1200) and the French fleurs-de-lis coat (1211) although the fleur-de-lis was present on royal robes and ornaments since at least 1179.
That Alfonso VII took the lion on his banners and arms was due to the dominance of León in the kingdom. When other parts of the Chronica refer to the raising the royal standards in the taken enemy fortress, it is referring to some flags which depicted the lion. It is disputed whether this animal represented to the monarch or kingdom, in the first case the strength of the sovereign but it seems a clearer identification between the words "Legio" and "leo" that would imply the adoption of the feline as image of the city and the kingdom. In favour of the second hypothesis is the fact that in the author of the Chronica made a rhyme with the words "legionis" and "leonis".