Ulrich L. Lehner (born 1976 in Straubing, Bavaria, Germany) is the Warren Foundation Professor of Theology at the University of Notre Dame. He is a trained theologian and historian.

After graduating from the Johannes-Turmair-Gymnasium [de] in Straubing in 1996 he received a B.A. in philosophy from the Munich School of Philosophy and a B.A. in theology from the Ludwig-Maximilians-Universität München in 1999, and a diploma in theology from the University of Munich in 2003. In 2006 he received his PhD in theology from the Universität Regensburg with a thesis on the concept of providence of Immanuel Kant and Protestant scholasticism. In 2015 the received the degree of habilitated doctor in history from the Central European University with his award-winning book Enlightened Monks; it was the first ever degree of its kind awarded at the CEU.

From 2006 to 2019 Lehner was professor of historical theology and religious history at Marquette University in Milwaukee.

In 2013 he declined a job offer for a professorship in German Literature at the University of Kansas and in 2019 for the Warren Chair at Duke Divinity School. Since July 2019 he is the William K. Warren Foundation professor of theology at the University of Notre Dame.

The bulk of his research is focused on the religious and cultural history spanning from the Renaissance era to the current times. His groundbreaking research on the Catholic Enlightenment has received international acclaim and established him as a leading authority on the subject. In 2022 his book The Inner Life of Catholic Reform proposed an integrative approach to consider spiritual factors in the study of the Counter-Reformation and Catholic Reform. Historian Carlos Eire praised this book as "a brilliant interweaving of cultural, intellectual, and social history reminiscent of the best histoire total produced by the Annales school." In recent years, Lehner has shifted his focus to historical studies on race and religion, particular the history of his own ethnic heritage, the Romani, and the history of sexuality.

Since 2013 he has penned several studies on clergy crimes, uncovering century old patterns of secrecy and deception about violent and sexual abuse. In 2023 he published a monograph on sexual crimes in the pre-1773 Society of Jesus, entitled Staged Chastity, which has also attracted international attention. His biography of Rudolf von Gerlach, which was praised for its gripping narrative style and detailed analysis, appeared in 2025.

Lehner has contributed in a variety of publications to the history of academic freedom, the history of gender and sexuality, the history of sexual abuse in the Catholic Church, and the relationship between Catholic thinkers and German Nazi ideology. Recently, he has been advocating for the usefulness of Nicolai Hartmann's ontology in the field of history. In 2023 he suggested a "synodal hermeneutic" for historical theology, demonstrating support for the reform agenda of Pope Francis' Synod on Synodality.

Lehner's publications have been translated into seven foreign languages.