Gluco-azoles competitively inhibit glucosidases by transition-state mimicry and their ability to interact with catalytic acid residues in glucosidase active sites. We noted that no azole-type inhibitors described, to date, possess a protic nitrogen characteristic for 1H-imidazoles. Here, we present gluco-1H-imidazole, a glucoazole bearing a 1H-imidazole fused to a glucopyranose-configured cyditol core, and three dose analogues as new glucosidase inhibitors. All compounds inhibit human retaining beta-glucosidase, GBA1, with the most potent ones inhibiting this enzyme (deficient in Gaucher disease) on a par with glucoimidazole. None inhibit glucosylceramide synthase, cytosolic beta-glucosidase GBA2 or alpha-glucosidase GAA. Structural, physical and computational studies provide first insights into the binding mode of this conceptually new class of retaining beta-glucosidase inhibitors.