The Sun of May (Spanish: Sol de Mayo) is one of the national symbols of the Río de la Plata countries of Argentina and Uruguay, featured in their respective flags and coats of arms. while in the Uruguayan case it conforms to the convention of the European heraldry of 16 rays. Since the forces of Buenos Aires were occupying the city of Potosí in Alto Perú at that time, the Assembly of Year XIII also decided that the Spanish real coinage made at the Mint of Potosí should change its design. The legislators determined that the obverse of the new coins should have the seal of the assembly but without the rising sun, which instead appeared in its entirety on the reverse, a sign of the importance it had as a symbol of the new nation. as the most widespread explanation states it represents Inti, the solar god of the Incas. The supposed Inca origin of the symbol is often related to the fact that the national coat of arms was made by Juan de Dios Rivera, a goldsmith of Inca descent originally from Cusco but based in Buenos Aires. For this reason, he is regarded by some as the creator of the Sun of May. However, there are no primary sources to confirm this, In reality, Rivera followed the instructions he received from the government, and recent research has demonstrated the existence of a French revolutionary emblem from late 18th century that served as a model for the seal.
thumb|upright|The ornamented royal coat of arms of the [[Kings of Spain during the Bourbon era, featuring a sun alongside the motto "a solis ortu usque ad occasum".]]
Although widely accepted, the supposed Inca origin of the Sun of May lacks contemporary sources and emerged only with the development of the country's historiography. The absence of a standardized sun design was evident in numismatics as well, as most provincial coinage featured varied sun designs, except the coins from La Rioja, which replicated the 1813 and 1815 Potosí coins. The decree also determines those authorized to use the flag with sun, allowing individuals to use only the flag without sun. At the end of that year, the new state adopted its first official flag, composed of 9 white stripes alternated with 9 light blue stripes (in reference to the nine departments that composed the country at the time) and the Sun of May in the upper left corner, taking the symbolism of the Argentine independence. The law also determined that the design of the sun should be the same as that of the national coat of arms.