Purpose: To investigate the influence of connector diameter on the mechanical load to fracture in monolithic three-unit lithium disilicate fixed partial dentures (FPDs). Materials and Methods: A total of 24 FPDs were designed and manufactured using computer-aided design/computer-assisted manufacturing (CAD/CAM) with connector diameters of 16 mm2, 12 mm2, or 9 mm2 (Groups A, B, and C, respectively; n = 8 for each group). After thermal and mechanical aging, the FPDs were subjected to mechanical load-to-fracture assessment. Results: Fracture loads of Groups B (834 ± 105 N) and C (796 ± 41 N) were significantly lower compared to Group A (990 ± 65 N). Conclusion: Connector dimensions proved to be crucial for fracture resistance of monolithic lithium disilicate FPDs.