Gas-phase reactions between silane (SiH4) and water (H2O) were investigated using ab initio calculations at the CCSD(T)/6-311++G**//MP2/6-31+G* level. Within the energy range of 160 kcal/mol, we located 40 equilibrium and 27 transition states on the potential energy surfaces of the Si-O-H systems. Over an energy barrier of 46.61 kcal/mol, the weakly bonded molecular complex SiH4-H2O can eliminate first H-2 molecule and produce silanol (SiH3OH). The transition state is a dihydrogen-bonded structure with retention of the silane configuration. The total energy of the direct products SiH3OH + H-2 is -10.83 kcal/mol relative to the reactants. Over an energy barrier of 58.09 kcal/mol, SiH4-H2O can eliminate first H-2 and produce a transient dative bonded complex SiH2-H2O. Providing more energy to the system, SiH4-H2O can dissociate atomically and the initial products can further eliminate H-2 or H, producing smaller species including molecules SiH-OH, SiH2-O, Si-H2O, and SiO and radicals SiH2-OH, SiH-H2O, HSiO, and HOSi.