Items were generated to explore the factorial structure of a construct of fundamentalism worded appropriately for Judaism, Christianity, and Islam. Results suggested three underlying dimensions: External versus Internal Authority, Fixed versus Malleable Religion, and Worldly Rejection versus Worldly Affirmation. The three dimensions indicate that religious fundamentalism is a personal orientation that asserts a supra-human locus of moral authority, context unbound truth, and the appreciation of the sacred over the worldly components of experience. The 15-item, 3-dimension solution was evaluated across Mexican (...) and American samples. Fit indexes point out the viability of the new inventory across these two samples henceforward referred to as the Multi-Dimensional Fundamentalism Inventory. Additional validity tests supported that the new inventory was negatively correlated with participants’ integrative complexity in a religious domain–specific way. (shrink)