The Monarchy of Spain, constitutionally referred to as The Crown and commonly referred to as the Spanish monarchy or (historically) Hispanic Monarchy, is a constitutional institution and a historic office of Spain. The monarchy comprises a reigning King or Queen of Spain, their family, and the royal household organization which supports and facilitates the monarch in the exercise of his royal duties and prerogatives. The monarchy is currently represented by King Juan Carlos I, his wife Queen Sofia, and their children and grandchildren. Opinion polls routinely reveal that the monarchy remains popular by a wide majority of citizens in contemporary Spain, with as many as 75% of Spanish citizens ranking the monarchy above any other public institution in the country. In 2010, the budget for the Spanish monarchy was 7.4 million euros, one of the lowest public expenditures for the institution of monarchy in Europe.

The Spanish Constitution of 1978 reestablished a constitutional monarchy as the form of government for Spain. The 1978 constitution affirmed the role of the King of Spain as the personification and embodiment of the Spanish State and a symbol of Spain's enduring unity and permanence. Constitutionally, the king is the head-of-state and commander-in-chief of the Spanish Armed Forces. The constitution codifies the use of royal styles and titulary, royal prerogatives, hereditary succession to the crown, compensation, and a regency-guardianship contingency in cases of the monarch's minority or incapacitation. According to the constitution, the monarch is also instrumental in promoting Ibero-American relations, the "nations of its historical community". In this capacity, the King of Spain serves as the president of the Ibero-American States Organization, representing over 700,000,000 people in twenty-four member nations worldwide. In 2008, Juan Carlos I was considered the most popular leader in all Ibero-America.

The Catholic Monarchs (Spanish: Reyes Católicos) is the joint title used in history for Queen Isabella I of Castile and King Ferdinand II of Aragon. They were both from the House of Trastámara and were second cousins, being both descended from John I of Castile; they were given a papal dispensation to deal with consanguinity by Sixtus IV. The title of "Catholic King and Queen" was bestowed on them by the Pope Alexander VI in 1496, for defending Catholic dogmas within their realms. They married on October 19, 1469, in the city of Valladolid; Isabella was eighteen years old and Ferdinand a year younger. Their marriage united both crowns under the same family. John Elliot and many other historians consider that the unification of Spain can essentially be traced back to the marriage of Ferdinand and Isabella, but newer historical opinions recognize that under their rule Spain was still a composite monarchy. Castile and Aragon remained largely separate entities for decades to come. 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 Spanish Civil War was a major conflict fought in Spain from 17 July 1936 to 1 April 1939. The war began after a pronunciamiento (declaration of opposition) by a group of generals under the leadership of José Sanjurjo against the elected government of the Second Spanish Republic, at the time under the leadership of President Manuel Azaña. The rebel coup was supported by a number of conservative groups including the Spanish Confederation of the Autonomous Right, monarchists such as the religious conservative Carlists, and the Fascist Falange. The uprising was authoritarian and anti-separatist in inspiration; anti-Basque and anti-Catalan feeling marked the Nationalist zone.

Following the only partially successful coup, Spain was left militarily and politically divided. From that moment onwards, general Francisco Franco began a protracted war of attrition against the established government for the control of the country. The rebel forces received the support of Nazi Germany and the Kingdom of Italy, as well as neighbouring Portugal, while the Soviet Union and Mexico intervened in support of the Republican government or loyalist side.