John of Ragusa (Croatian: Ivan Stojković; born c. 1380 at Dubrovnik, Republic of Ragusa) was a Croatian Dominican theologian. He died at Lausanne, Switzerland in 1443.
He was president of the Council of Basle, and a legate to Constantinople. He was created cardinal by Antipope Felix V, so would be considered by many a "pseudocardinal".
He entered the Dominican Order and devoted himself to the observance of the rule of his order and the study of the sacred sciences. By reason of his great attainments in theology, Scripture, and the Oriental languages, he was considered an oracle in his native Dalmatia.
In 1420 he became a master of theology at the University of Paris.
In the year 1426 he was appointed procurator general of the Dominican Order, and went to reside at Rome under Pope Martin V. There he received marks of honour and esteem from the pope and the College of Cardinals, and the former eventually named him papal theologian for the General Council of Basle. John was, moreover, chosen to open the council, in place of Cardinal Julian Cesarini, who was detained by other business.
Arriving at Basle on 19 May 1431, he on the same day arranged with the Bishop of Basle for the opening of the council on the 23rd of the same month. The opening did not take place, however, until 23 July 1431, in the cathedral church, when John preached from the text: "Et angelus testamenti, quem vos vultis. Ecce venit" (Mal., iii, 1). In the council he exonerated the absent cardinals from the charge of contempt (Feb., 1433). On eight mornings he spoke against the doctrines of the Hussites.
Having been sent as a legate of the council to Constantinople to urge the reunion of the Eastern and Western Churches, John of Ragusa induced the Emperor John Paleologus and the Patriarch Joseph to send an embassy to the council through the treaty which they made with Pope Eugenius IV was broken by the Greeks. John afterwards sojourned at Constantinople to study the Greek language and to become better acquainted with the situation of ecclesiastical affairs.