Cardinal Gerhard Ludwig Muller served as prefect of the Congregation for the Doctrine of the Faith from 2012 to 2017. He was appointed bishop of Regensburg, Germany, in 2002 by Pope John Paul II. Muller was elevated to archbishop in 2012 by Pope Benedict XVI and to cardinal in 2014 by Pope Francis.

Prior to being named prefect, Muller served on the Pontifical Council for Culture, Congregation for Catholic Education, and the Pontifical Council for Promoting Christian Unity. After Muller 's appointment as archbishop and prefect, he also became ex officio;president of the Pontifical Biblical Commission, the International Theological Commission, and the Pontifical Commission Ecclesia Dei.

Muller retired in 2017. He has written more than six hundred works on various topics including dogmatic theology, revelation, ecumenism, and the diaconate. He is the editor of the Complete Works of Joseph Ratzinger--Pope Benedict XVI in sixteen volumes.