Karl Borromäus Adam was a German Catholic theologian of the early 20th century.

Adam was born in Bavaria in 1876. He attended the Philosophical and Theological Seminary at Regensburg and was ordained in 1900. Adam spent the next two years doing parish work. Adam received his doctorate at the University of Munich in 1904.

In 1915, he became a professor of theology in Munich. Two years later, he accepted a chair in moral theology at Strasbourg and in 1919 he went to teach dogmatic theology at the University of Tübingen. He retired from that post in 1949.

Adam wrote extensively on theology. His books include: Tertullian's Concept of the Church, Eucharistic Teaching of St. Augustine, Christ Our Brother, The Son of God, The Spirit of Catholicism, Roots of the Reformation and One And Holy.

Adam is best known for his 1924 work, The Spirit of Catholicism. It has been widely translated, and is still in print today. In The Spirit Of Catholicism, Adam communicates with the laity about the Catholic faith and the Church's role as the keeper of the faith.