Karl Stern (April 8, 1906 - November 11, 1975) was a German Canadian neurologist and psychiatrist, and a Jewish convert to the Catholic Church.

There was no synagogue or rabbi in the town, and although regular services and classes were held under the direction of a cantor, Stern's religious education was minimal.

As a teenager he sought to re-engage with the Jewish faith, and began attending an Orthodox synagogue, but he soon became an atheist Zionist.

In 1943, after much soul-searching, and ultimately influenced by encounters with Jacques Maritain and Dorothy Day, Stern converted to Christianity and was baptized as a Roman Catholic.

Stern married Liselotte von Baeyer, a bookbinder (died 1970) and they had four children: Antony, a psychiatrist (1937-1967), Katherine Skorzewska, Michael and John.