John, the name given him at Baptism, was born in Moravia into a poor family, the ninth of 12 children. Although he longed to be a priest there was no money for studies, and he was apprenticed to a baker. But God guided the young man's fortunes. He found work in the bakery of a monastery where he was allowed to attend classes in its Latin school. After the abbot there died, John tried the life of a hermit but when Emperor Joseph II abolished hermitages, John again returned to Vienna and to baking. One day after serving Mass at the cathedral of St. Stephen, he called a carriage for two ladies waiting there in the rain. In their conversation they learned that he could not pursue his priestly studies because of a lack of funds. They generously offered to support both him and his friend, Thaddeus, in their seminary studies. The two went to Rome, where they were drawn to St. Alphonsus' vision of religious life and to the Redemptorists. The two young men were ordained together in 1785.
Newly professed at age 34, Clement Mary, as he was now called, and Thaddeus were sent back to Vienna. But the religious difficulties there caused them to leave and continue north to Warsaw, Poland. There they encountered numerous German-speaking Catholics who had been left priestless by the suppression of the Jesuits. At first they had to live in great poverty and preached outdoor sermons. They were given the church of St. Benno, and for the next nine years they preached five sermons a day, two in German and three in Polish, converting many to the faith. They were active in social work among the poor, founding an orphanage and then a school for boys.
Drawing candidates to the congregation, they were able to send missionaries to Poland, Germany and Switzerland. All of these foundations had eventually to be abandoned because of the political and religious tensions of the times. After 20 years of difficult work Clement himself was imprisoned and expelled from the country. Only after another arrest was he able to reach Vienna, where he was to live and work the final 12 years of his life. He quickly became "the apostle of Vienna," hearing the confessions of the rich and poor, visiting the sick, acting as a counselor to the powerful, sharing his holiness with all in the city. His crowning work was the establishment of a Catholic college in his beloved city.
Persecution followed him, and there were those in authority who were able for a while to stop him from preaching. An attempt was made at the highest levels to have him banished. But his holiness and fame protected him and the growth of the Redemptorists. Due to his efforts, the congregation, upon his death in 1820, was firmly established north of the Alps.
He was canonized in 1909.