This Special Issue covers key aspects of coeliac disease (CD) research, from epidemiology to diagnostic methods, dietary management, and associated diseases. Diagnostics are central, with studies supporting rapid anti-tTG-IgA tests and the celiac lymphogram (TCR-γδ+ IELs) in complex cases. CD often coexists with microscopic colitis (MC) and eosinophilic esophagitis (EoE), complicating care. Low-FODMAP diets may help with non-responsive CD cases, but a gluten-free diet remains essential.