Three major theories could potentially explain why hygiene norms vary across societies: tightness-looseness theory, disease threat theory, and theory of a civilizing process driven by how self-control is valued. We test these theories using data from a study of 56 countries across the globe, in which almost 20,000 participants reported their norms about spitting in six different contexts, hand washing in six different contexts, and tooth brushing. Participants also reported the perceived tightness of their society, whether they perceived diseases as a threat to their society, and their valuation of self-control. In support of the civilizing process, most of the norms in our study (including most hand washing norms and most spitting norms) were stricter in countries where self-control is valued more highly. A few norms did not follow this main pattern and these norms were instead stricter in countries where disease was perceived as a greater threat. Thus, while the theory of a civilizing process received the strongest support, our data indicate that some combination with the disease threat theory may be required to fully explain country-variation in hygiene norms.