The reaction showed first-order kinetics with respect to the glycosyl donor and acceptor. Moreover, we also found that the reaction rate is dependent on the catalyst concentration. In conclusion, we describe the first application of trisubstituted selenonium salts for the direct stereoselective synthesis of deoxyglycosides directly from hemiacetals, obviating the need for anomeric functionalization. The reaction conditions are mild and compatible with most common protecting groups. A step-wise process which involves the in situ formation of a chalgonenium/OH complex that catalyses the key H + transfer to the OH on the hemiacetal to generate a transient oxocarbenium ion is proposed. This short-lived intermediate quickly colapses into the acetal product upon reaction with the available activated nucleophile in the reaction. This study opens new avenues for developing mild non-metallic acid/base catalysis for the stereoselective synthesis of complex glycosides and highlights the potential of chalcogenonium salts as a new class of catalysts for challenging glycosylation chemistry.