This is a list of the individuals who were, at any given time, considered the next in line to inherit the throne of Spain, should the incumbent monarch die. Those who actually succeeded (at any future time) are shown in bold.
From the personal union of the Crown of Castile and the Crown of Aragon until the accession of the first Bourbon monarch in 1700, the heir to the Spanish throne was the person closest to the Spanish monarch according to the male-preference cognatic primogeniture. From the accession of Philip V until the Pragmatic Sanction of 1830, the heir to the Spanish throne was the person closest to the Spanish monarch according to the Salic law. The heir, whether heir apparent or heir presumptive, was often granted the title of Prince of Asturias.
Significant breaks in the succession, where the designated heir did not in fact succeed (due to usurpation, conquest, revolution, or lack of heirs) are shown as breaks in the table below.