William Kilpatrick is an American author, columnist, and retired educator known for his writings on Christianity, Islam, secularism, and cultural issues from a conservative Catholic perspective. He taught English for many years at Boston College High School in Boston, Massachusetts, before retiring to focus on writing and lecturing. Kilpatrick holds a B.A. from the University of New Hampshire and an M.A. from the University of Massachusetts, both in English. He contributes regularly to Catholic publications such as Crisis Magazine, LifesiteNews, and The Catholic World Report, where he has written positively about David Wood's YouTube ministry critiquing Islam. He has also written for conservative outlets like FrontPage Magazine and American Thinker.

Kilpatrick is the author of several books, including 'Christianity, Islam, and Atheism: The Struggle for the Soul of the West' (2012), 'The Politically Incorrect Guide to Islam (and the Crusades)' (2013), 'Infiltration: The Plot to Destroy the Church from Within' (2015), and 'The Devil and Bella Dodd: Orthodoxy, Communism, and the Infiltration of the Catholic Church' (2020). His works often argue against what he sees as threats to Western Christian civilization from Islam, atheism, communism, and progressive ideologies within the Church.

Kilpatrick's commentary has been controversial for its strong critiques of Islam and modern Catholicism, drawing both praise from traditionalist Catholics and criticism from those accusing him of Islamophobia. He has appeared as a speaker at events for organizations like Turning Point USA and Acton Institute.