Juan Carlos I (baptized as Juan Carlos Alfonso Víctor María de Borbón y Borbón-Dos Sicilias; born 5 January 1938, Rome, Italy) is the reigning King of Spain. He is the son of the late Infante Juan, Count of Barcelona and the late Princess María Mercedes of Bourbon-Two Sicilies. He is the grandson of the prior King of Spain, Alfonso XIII who was deposed in 1931.

On 22 November 1975, two days after the death of Francisco Franco, Juan Carlos was designated King according to the law of succession promulgated by Franco. The Spanish throne had been vacant for thirty years in 1969 when Franco named Juan Carlos as the next ruler of Spain.

King Juan Carlos successfully oversaw the transition of Spain from dictatorship to parliamentary democracy. Polls from 2000 show that he is widely approved of by Spaniards. In 2008 he was considered the most popular leader in all Ibero-America.