Born in Vienna to Lutheran Protestant parents, with his father being a baker, Melchior Klesl studied philosophy at the University of Vienna, and was with his parents converted by the court chaplain, Father Georg Scherer, S.J. He received minor orders in 1577, when he was assigned a canonry, and, even while in minor orders, he preached and held conferences at Korneuburg and in the vicinity, making many conversions. In 1579 he became doctor of philosophy and provost of St. Stephen's in Vienna, which dignity carried with it the chancellorship of the university, and was finally ordained to the priesthood. As early as the following year he was appointed councillor of the Bishop of Passau for Lower Austria. Rudolf II, impressed by the vigour and success of his campaign against Protestantism, entrusted him with the work of the Counter-Reformation, which became his life work. Klesl brought back into the fold the cities of Baden, Krems, and Stein, though not without great difficulty, nor indeed without actual risk of his life. In 1585 he was made imperial councillor by Rudolf II, who three years later appointed him court chaplain and administrator of the Diocese of Wiener Neustadt. It took him but a very short time to restore the Catholic rule in this thoroughly disorganized bishopric. He was compelled in doing so to be constantly on his guard against the monastic council, which, in a memorial on the subject, he calls, "the cause of all evil, the champion of godless prelates and priests against their bishop, a parasite". In 1598 Klesl was named Bishop of Vienna, a diocese which was spiritually and materially in a state of degradation. On 30 Mar 1614, he was consecrated bishop by Placido della Marra, Bishop of Melfi e Rapolla. He received the purple from Paul V in 1616. In 1611 Matthias placed Klesl at the head of his privy council. As such he held full sway in the government, stoutly opposing the concessions to the Hungarian Protestants in 1606. He assisted to secure the election of Matthias to the imperial throne, and sought, but without success, to strengthen the new emperor's position by making peace between the Catholics and the Protestants. When during the short reign of Matthias the question of the imperial succession demanded prompt attention, the bishop, although quite as anxious as his opponents to retain the empire in the house of Habsburg and to preserve the dominance of the Roman Catholic Church, advised that this question should be shelved until some arrangement with the Protestant princes had been reached. This counsel was displeasing to Archduke Maximilian of Tyrol and to Archduke Ferdinand of Styria, who after the Oñate treaty became King of Bohemia and Holy Roman Emperor as Ferdinand II. They believed that Klesl was hostile to the candidature of the latter prince. It was, however, impossible to shake his influence with the emperor. In June 1618, a few months before the death of Matthias, the Bohemian Estates, having thrown their governor out of the window of the palace at Prague for the second time, broke out into open rebellion. Klesl could not be induced to take energetic measures against them and was seized by order of the archdukes and imprisoned at Schloss Ambras in Tyrol. A short time later he was formally arrested by Cardinal Fabrizio Verospi and brought to the castle of Innsbruck, whence he was transferred to the monastery of St. Georgenberg in 1619. In November 1622, Rome, Italy became his place of confinement by order of Pope Gregory XV. He was granted his freedom by the emperor in June of the following year, but was to remain in Rome. Klesl lived to enjoy the satisfaction of seeing himself solemnly brought back to Vienna on 25 January 1628, and reinstated as bishop, but without any political influence. He decreed that the Feast of the Immaculate Conception on 8 December be henceforth observed in his dioceses "in the same manner as Sundays and other prescribed holy days", and in spite of the nuncio's protestation, he strove to maintain the peculiarly Viennese custom whereby Holy Communion was distributed on Good Friday. He died in Wiener Neustadt in 1630. His heart reposes before the high altar of the cathedral of Wiener Neustadt while his body rests in the cathedral of St. Stephen's, Vienna. Inhabitants of Vienna will recognize Klesl's name first and foremost because Khleslplatz in Vienna's 12th district, Meidling, in the former village of Altmannsdorf, has been named after the cardinal, allegedly because he used to stop at No.12 on his journeys from Wiener Neustadt to Vienna. Since 1978, the 16th century building has housed the Renner-Institut, the political academy of the Social Democratic Party of Austria, while No.6 was, until 1998, the site of the Tierschutzhaus of the Wiener Tierschutzverein, where generations of animal lovers would go to collect homeless pets.
Episcopal succession
While bishop, he was the principal consecrator of:
