Berkeleyan idealism, or ‘immaterialism,’ has had an enormous impact on the history of philosophy during the last three centuries. In recent years, Christian scholars have been especially active in exploring ways that Berkeley's thesis may be fruitfully applied to a variety of issues in philosophy and theology. This essay provides an overview of some of the ways Christian philosophers have deployed immaterialism to solve problems and generate insights in metaphysics, philosophy of mind, philosophy of science, philosophy of religion, and philosophical theology.