This Element leverages a comparative approach to understand how conspiracy theories and their believers differ within and across countries. Using original survey data from eight varied cases (Australia, Brazil, Canada, Germany, Lebanon, Morocco, South Africa, and the United States) the authors present specific contemporary conspiracy theories, illustrate how these theories appeal in their national context, and determine whether the characteristics of the typical conspiracy theory believer vary across setting. They first demonstrate that there is a wide range of conspiracy theories, some of which have worldwide reach, whereas others are more context specific. Then, they show that the determinants of individual conspiracism are very similar in the Western world and Brazil, but do not necessarily travel to Lebanon, Morocco and South Africa. Lastly, they summarize the main conclusions of this Element and discuss the need for greater comparative research on conspiracy theories and propose clear areas for future research.