JOHN IV. (pope from 640 to 642) was a Dalmatian by birth, and succeeded Severinus after the papal chair had been vacant four months. While he adhered to the repudiation of the Monothelitic doctrine by Severinus, he endeavoured to explain away the connexion of Honorius I. with the heresy. His successor was Theodorus I.

JOHN IV., Lascaris, emperor of Nicaea, son of Theodore II., was born about 1250. His father dying in 1258, Michael Palaeologus conspired shortly after to make himself regent, and in 1261 dethroned the boy monarch and put out his eyes. John died in prison.

JOHN IV. (1603-1656), “the Fortunate,” of Portugal, was born at Villaviciosa in March 1603, succeeded to the dukedom of Braganza in 1630, and married Luisa de Guzman, eldest daughter of the duke of Medina Sidonia, in 1633. By the unanimous voice of the people he was raised to the throne of Portugal (of which he was held to be the legitimate heir) at the revolution effected in December 1640 by a conspiracy of the nobles against the grievances inflicted by Spain and the insolence of Philip IV.’s minister, the duke of Olivarez. His accession ultimately led to a protracted war with Spain, of which the final issue—the recognized independence of Portugal—did not declare itself until a subsequent reign (1668). He died after a prosperous reign of sixteen years, on November 6, 1656, and was succeeded by his son Alphonso VI.