Katherine Stewart is an American journalist and author who often writes about issues related to the separation of church and state, the rise of religious nationalism, and global movements against liberal democracy.

Her books include The Good News Club: The Christian Right's Stealth Assault on America's Children (2012), The Power Worshippers: Inside the Dangerous Rise of Religious Nationalism (2020), which also served as the basis for the documentary film God & Country (2024); and the forthcoming Money Lies and God: Inside the Movement to Destroy American Democracy.

[13] In a March 2020 op-ed, she linked the slow federal response to the country's coronavirus outbreak to President Trump's connections to the far right and anti-science conservatives.

"[27] Alexander Heffner of the Minnesota Star Tribune wrote that the book "exposes the violation of church and state in schools", calling it "an important work" and "a fascinating exposé", and Stewart "a great digger for facts" and "a respectful narrator.

[4][34][35] Power Worshippers also served as the basis for God & Country (2024), a documentary film directed by Dan Partland and produced by Rob Reiner.