Crown prince of Spain, son of Philip II., born at Valladolid in 1545, died in prison at Madrid in July, 1568. He was sickly, and as he grew up was subject to violent bursts of passion, which his father hoped would be subdued by the discipline of the university at Alcala. But as this proved of no avail, he was considered unfit for the throne, and in 1563 his cousins, the archdukes Rudolph and Ernest of Austria, were appointed in his stead presumptive heirs to the crown. When Alva was appointed in 1567 governor of Flanders, a post to which Don Carlos had aspired, the prince's exasperation led him to plan an assault upon his father, and to perpetrate one upon his uncle Don Juan, in consequence of which he was put under arrest, Jan. 18, 1568, and subsequently transferred to the prison where he died. His death as well as his life gave rise to many conflicting rumors. It has been commonly believed until recently that he was put to death by order of his father; but recent historians have shown that he was insane, and died of a fever brought on by his own extravagance in diet and exposure.

The incompatibility of temper between a rigid, iron-hearted man like King Philip, and a morbid, impulsive youth like Don Carlos, the fact that the prince had been engaged to Elizabeth of France, who subsequently became his stepmother, his sympathy with the revolt of the Netherlands, and his hatred of Alva and the other ministers of his father, all conspired to invest the melancholy fate of the prince with a halo of romance, which has been poetically treated by Alfieri, Campistron, Otway, and others, and above all by Schiller. U. Carlos Maria Isidor, pretender to the crown of Spain, son of King Charles IV., born March 29, 1788, died in Trieste, March 10, 1855. Many of the opponents of the constitutional regime which was restored in 1820 gathered around Don Carlos, hoping that, after the decease of his childless brother Ferdinand VII., he would ascend the throne. When absolutism was reestablished in 1823, the most reactionary party leaders, and especially the representatives of the clerical interest, continued to cluster around him. But their hopes were frustrated by Ferdinand's marriage with Maria Christina, and by the abrogation of the Salic law, which placed Isabella upon the throne.

In 1832, when Ferdinand was supposed to be on the eve of death, the Carlists succeeded in extorting from him a decree reestablishing the Salic law, and thus excluding Isabella; but he recovered his health, and the fraud practised upon him was immediately redressed. In 1833, when Ferdinand died, Don Carlos proclaimed himself king. Maria Christina, the regent, branded him as a rebel, and concluded with Britain, France, and Portugal the so-called quadruple alliance, the practical effect of which was to expel Don Carlos and Dom Miguel, the champions of absolutism, from Spain and Portugal. On July 1, 1834, Don Carlos left England, whither he had fled, smuggled himself into Spain, and succeeded in kindling a civil war in the northern provinces, which raged for upward of six years. Don Carlos eluded the vigilance of his opponents till 1839, when he was compelled to seek refuge in France, where, upon his refusal to renounce his claims, he was by order of the French government detained at Bourges. The decree which ordained his perpetual expulsion from Spain was unanimously confirmed by the cortes in 183G. In 1845 he adopted the name of count of Molina, abdicated in favor of his eldest son the count of Montemolin, and on receiving permission to leave France took up his abode in Austria. HI. Carlos Luis Maria Fernando, son of the preceding, born Jan. 31, 1818, died at Trieste, Jan. 13, 1861. In 1846 he left Bourges, where he had resided with his father, and took up his abode in England under the name of the count of Montemolin. In April, 1849, he made an attempt to introduce himself in disguise into Spain, but he was arrested, detained from April 5 to the 10th in the citadel of Perpignan, and on April 15 he was again in London. In 1860 he entered Spain with 3,000 men, was defeated at Tor-tosa, and made prisoner.

He was soon set at liberty, upon renouncing his claim to the throne, but immediately retracted his renunciation. - His successor was his brother Don Carlos Juan Maria Isidor, born May 15, 1822, who in October, 1868, resigned his claims to the crown in favor of his son, Carlos Maria Juan Isidor, the present pretender (born March 30, 1848), in whose favor an active insurrection is now in progress (1873). Don Alfonso, brother of the pretender (born Sept. 12, 1849), is among his most active supporters.