UFC on ESPN 23: Reyes vs. Procházka was a mixed martial arts event produced by the Ultimate Fighting Championship that took place on May 1, 2021 at the UFC Apex facility in Enterprise, Nevada, part of the Las Vegas Metropolitan Area, United States. A light heavyweight bout between former UFC Light Heavyweight Championship challenger Dominick Reyes and former Rizin Light Heavyweight Champion Jiří Procházka served as the main event.

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