Mixing i-PrI and DABCO in solvent EtCN gave two quaternary ammonium salts (QASs) quantitatively, one of which is monocationic (QAS-1) and the other is dicationic (QAS-2). These QASs were found to catalyze hydrosilylation of alkynes with hydrosilanes (HAH) without the aid of metal and metalloid catalysts. This organocatalysis can be applied to a variety of alkynes: terminal/internal aryl and alkyl alkynes with/without a functional group. With dihydrosilanes (H₂Si), the HAH occurred with high E-selectivity through syn addition, which was exclusively observed when using terminal alkyl alkynes, irrespective of a hydrosilane used. A scalable HAH is also feasible. The H-Si unit remaining in alkenylsilanes derived from H₂Si is available for dehydrogenative alkynylation and N-heteroarylation under zinc-pyridine catalysis. This synthetic application delivers unique silicon compounds that have, for instance, alkyl, aryl, alkenyl, and alkynyl groups in a single molecule. Mechanistic studies suggested that alkynes activated by QASs irreversibly react with hydrosilanes that become more nucleophilic by the coordination of EtCN. A radical pathway is unlikely. The QAS catalysts can be recovered and reused at least 5 times.