What is the role of Wahhabism in the rise of global terrorism? Is Saudi Arabia and its Wahhabi ideology a contributing factor in the spread of violent radicalization in the Muslim world? What are the possible causal mechanisms linking Wahhabism to violence? How it is possible to ascertain these mechanisms and disentangle them from other sources of radicalization in the Muslim world? Three potential hypotheses may provide answers to these questions: (1) Wahhabism provides passive ideological support for extremism, but is not a sufficient cause of violent radicalization, (2) Wahhabism provides indirect support through the establishment of networks that give material facilitation to extremist groups, and (3) Wahhabism provides direct support to extremists with the approval of the Saudi government. The major finding of this study is that the first hypothesis-Wahhabism is a facilitator but not a direct contributor to violent extremism-is best supported by the evidence. Those who claim that Wahhabism has nothing to do with terrorism underestimate the extent to which the core principles of Wahhabism overlap with the extremist ideology of takfir, and its inherent intolerance toward other creeds can create fertile minds ready to demonize foreigners and even fellow Muslims who are non-Wahhabists. The second hypothesis receives hardly any evidential support, while the third hypothesis has no support at all and amounts to guilt by association.