The solid-state structure of a discrete chloride monohydrate species, [Cl(H2O)]-, is reported for the first time. It was isolated as a salt of the tris(dipropylamino)cyclopropenium cation and has been structurally characterized by X-ray and neutron diffraction. Infrared (IR), far-infrared, and Raman spectroscopic studies were also carried out. Additionally, the D2O and HDO isotopomers were investigated. Of the six fundamental vibrational modes, only the out-of-plane bend ν3 was not observed as it forms an IR- and Raman-inactive local mode phonon.