Ferdinand II of Aragon in the context of "Spanish Golden Age"

Charles V (24 February 1500 – 21 September 1558) was Holy Roman Emperor and Archduke of Austria from 1519 to 1556, King of Spain (as Charles I) from 1516 to 1556, King of Sicily and Naples from 1516 to 1554, and also Lord of the Netherlands and titular Duke of Burgundy (as Charles II) from 1506 to 1555. He was heir to and then head of the rising House of Habsburg. His dominions in Europe included the Holy Roman Empire, extending from Germany to northern Italy with rule over the Austrian hereditary lands and Burgundian Low Countries, and Spain with its possessions of the southern Italian kingdoms of Sicily, Naples, and Sardinia. In the Americas, he oversaw the continuation of Spanish colonization and a short-lived German colonization. The personal union of the European and American territories he ruled was the first collection of realms labelled "the empire on which the sun never sets".

Charles was born in Flanders to Habsburg Archduke Philip the Handsome, son of Maximilian I, Holy Roman Emperor and Mary of Burgundy, and Joanna of Castile, younger child of Isabella I of Castile and Ferdinand II of Aragon, the Catholic Monarchs of Spain. Heir of his grandparents, Charles inherited his family dominions at a young age. After his father's death in 1506, he inherited the Habsburg Netherlands in the Low Countries. In 1516 he became King of Spain as co-monarch of Castile and Aragon with his mother. Spain's possessions included the Castilian colonies of the West Indies and the Spanish Main, as well as Naples, Sicily, and Sardinia. At the death of his grandfather Maximilian in 1519, he inherited the Austrian hereditary lands and was elected as Holy Roman Emperor. He adopted the Imperial name of Charles V as his main title, and styled himself as a new Charlemagne.

Juan Ponce de León (c. 1474 – July 1521) was a Spanish explorer and conquistador known for leading the first official European expedition to Puerto Rico in 1508 and Florida in 1513. He was born in Santervás de Campos, Valladolid, Spain, in 1474. Though little is known about his family, he was of noble birth and served in the Spanish military from a young age. He first came to the Americas as a "gentleman volunteer" with Christopher Columbus's second expedition in 1493.

By the early 1500s, Ponce de León was a top military official in the colonial government of Hispaniola, where he helped crush a rebellion of the native Taíno people. He was authorized to explore the neighboring island of Puerto Rico in 1508 and to take office as the first Governor of Puerto Rico by appointment of the Spanish crown in 1509. While Ponce de León grew quite wealthy from his plantations and mines, he faced an ongoing legal conflict with Diego Colón, the late Christopher Columbus's son, over the right to govern Puerto Rico. After a long court battle, Colón replaced Ponce de León as governor in 1511. Ponce de León decided to follow the advice of the sympathetic King Ferdinand and explore more of the Caribbean Sea.

The Kingdom of Naples, officially the Kingdom of Sicily, was a state that ruled the part of the Italian Peninsula south of the Papal States between 1282 and 1816. It was established by the War of the Sicilian Vespers (1282–1302). Until then, the island of Sicily and southern Italy had constituted the "Kingdom of Sicily". When the island of Sicily revolted and was conquered by the Crown of Aragon, it become a separate kingdom also called the Kingdom of Sicily. This left the Neapolitan mainland in the possession of Charles of Anjou who continued to use the name "Kingdom of Sicily". Later, two competing lines of the Angevin family competed for the Kingdom of Naples in the late 14th century, which resulted in the murder of Joanna I at the hands of her successor, Charles III of Naples. Charles' daughter Joanna II adopted King Alfonso V of Aragon as heir, who would then unite Naples into his Aragonese dominions in 1442.

As part of the Italian Wars, France briefly ruled the territory in 1494 and at the beginning of the 16th century; it then went to war with Spain over the kingdom in 1502, a conflict that ended in a victory for Ferdinand II, who was in full control of the kingdom by 1504. The Spanish held control of Naples throughout the 17th century where it remained an important source of economic and military power for the Spanish Crown. After the War of the Spanish Succession in the early 18th century, the possession of the kingdom again changed hands; the 1714 Treaty of Rastatt saw Naples given to Charles VI of the Austrian Habsburgs. However, Naples and Sicily were conquered by Charles, Duke of Parma (of the Spanish Bourbons) during the War of the Polish Succession in 1734, he was then installed as King of Naples and Sicily from 1735. In 1816, Naples formally unified with the island of Sicily to form the Kingdom of the Two Sicilies.

Catherine of Aragon (also spelt as Katherine,historical Spanish: Catharina, now: Catalina; 16 December 1485 – 7 January 1536) was Queen of England as the first wife of King Henry VIII from their marriage on 11 June 1509 until its annulment on 23 May 1533. She had previously been Princess of Wales while married to Henry's elder brother, Arthur, Prince of Wales, for a short period before his death.

Catherine was born at the Archbishop's Palace of Alcalá de Henares, and was the youngest child of Isabella I of Castile and Ferdinand II of Aragon. She was three years old when she was betrothed to Arthur, the eldest son of Henry VII of England. They married in 1501, but Arthur died five months later. Catherine spent years in limbo, and during this time, she held the position of ambassador of the Aragonese crown to England in 1507, the first known female ambassador in European history. She married Henry VIII shortly after his accession in 1509. For six months in 1513, she served as regent of England while Henry was in France. During that time the English defeated a Scottish invasion at the Battle of Flodden, an event in which Catherine played an important part with an emotional speech about courage and patriotism.

The Catholic Monarchs were Queen Isabella I of Castile (r. 1474–1504) and King Ferdinand II of Aragon (r. 1479–1516), whose marriage and joint rule marked the de facto unification of Spain. They were both from the House of Trastámara and were second cousins, as they were both descended from John I of Castile. To remove the obstacle that this consanguinity would otherwise have posed to their marriage under canon law, they were given a papal dispensation by Sixtus IV. They married on October 19, 1469, in the city of Valladolid; Isabella was 18 years old and Ferdinand a year younger. Most scholars generally accept that the unification of Spain can essentially be traced back to the marriage of Ferdinand and Isabella. Their reign was called by W.H. Prescott "the most glorious epoch in the annals of Spain."

Spain was formed as a dynastic union of two crowns rather than a unitary state, as Castile and Aragon remained separate kingdoms until the Nueva Planta decrees of 1707–1716. The court of Ferdinand and Isabella was constantly on the move in order to bolster local support for the crown from local feudal lords. The title of "Catholic King and Queen" was officially bestowed on Ferdinand and Isabella by Pope Alexander VI in 1494, in recognition of their defence of the Catholic faith within their realms.

The Tempietto del Bramante is a martyrium designed by Donato Bramante to commemorate the site traditionally regarded as the location of Saint Peter’s crucifixion. The small, freestanding chapel was commissioned by Ferdinand II of Aragon and Isabella I of Castile and was completed c. 1502 for the cloister of San Pietro in Montorio in Rome, Italy. The structure is considered a masterpiece of High Renaissance architecture, with scholars and architects noting Bramante’s harmonious proportions and his symbolic adaptation of Classical and early Christian architectural elements.

Joanna of Castile (6 November 1479 – 12 April 1555), historically known as Joanna the Mad (Spanish: Juana la Loca), was the nominal queen of Castile from 1504 and queen of Aragon from 1516 to her death in 1555. She was the daughter of Queen Isabella I of Castile and King Ferdinand II of Aragon. Joanna was married by arrangement to the Austrian archduke Philip the Handsome on 20 October 1496. Following the deaths of her elder brother John, elder sister Isabella, and nephew Miguel between 1497 and 1500, Joanna became the heir presumptive to the crowns of Castile and Aragon. When her mother died in 1504, she became queen of Castile. Her father proclaimed himself governor and administrator of Castile.

In 1506, Joanna's husband Philip became king of Castile jure uxoris as Philip I, initiating the rule of the Habsburgs in the Spanish kingdoms. Philip died that same year. Despite being the ruling queen of Castile, Joanna had little effect on national policy during her reign as she was declared insane and confined in the Royal Palace in Tordesillas under the orders of her father, who ruled as regent until his death in 1516, when she inherited his kingdom as well. Her son Charles I became king, and during his reign Joanna was nominally co-monarch but remained confined until her death. Joanna died aged 75 in 1555, at which point her son Charles, the Holy Roman Emperor, became the sole ruler of Castile and Aragon.

Isabella I (Spanish: Isabel I; 22 April 1451 – 26 November 1504), also called Isabella the Catholic (Spanish: Isabel la Católica), was Queen of Castile and León from 1474 until her death in 1504. She was also Queen of Aragon from 1479 until her death as the wife of King Ferdinand II. Reigning together over a dynastically unified Spain, Isabella and Ferdinand are known as the Catholic Monarchs. Her reign marked the end of Reconquista and also the start of Spanish Empire and dominance of Spain over European politics for the next century.

Isabella's marriage to Ferdinand of Aragon in 1469 created the basis of the de facto unification of Spain. With Ferdinand's help, she won the War of the Castilian Succession, securing her position as Queen of Castille. Isabella reorganized the governmental system, brought the crime rate down, and unburdened the kingdom of the debt which her half-brother King Henry IV had left behind. Her reforms and those she made with her husband had an influence that extended well beyond the borders of their united kingdoms.