Infrared spectra of representative LnH(1-4) lanthanide hydride molecules are observed in solid argon following reactions of the laser-ablated metal atoms with H-2. The LnH(2) dihydride is the major product and a stable (H-2)LnH(2) complex is observed for Ce and Pr. In addition, bands are also assigned to bridging hydrogen motions of several (LnH)(2) dimers. Supplementary density functional calculations of the lanthanide hydride reaction products reproduce general features of the spectra. Spectra of isolated molecular EuH2 and solid stoichiometric EuH2 reveal close correspondence, lending support to the molecular assignment and, by extrapolation, providing benchmark infrared frequencies for other lanthanide hydride solids based on their respective molecular vibrational modes.