Numerous studies show biblicist Christianity, religiosity, and conservative political identity are strong predictors of Americans holding skeptical attitudes toward publicly controversial aspects of science, such as human evolution. We show that Christian nationalismāmeaning the desire to see particularistic and exclusivist versions of Christian symbols, values, and policies enshrined as the established religion of the United Statesāis a strong and consistent predictor of Americansā attitudes about science above and beyond other religious and political characteristics. Further, a majority of the overall effect of political ideology on skepticism about the moral authority of science is mediated through Christian nationalism, indicating that political conservatives are more likely to be concerned with particular aspects of science primarily because they are more likely to be Christian nationalists. Likewise, substantial proportions of the wellādocumented associations between religiosity and biblical āliteralismā with views of science are mediated through Christian nationalism. Because Christian nationalism seeks to establish a particular and exclusivist vision of Christianity as the dominant moral order, adherents feel threatened by challenges to the epistemic authority undergirding that order, including by aspects of science perceived as challenging the supremacy of biblicist authority.