We have recorded the rotationally resolved infrared spectrum of the weakly bound Mn+-H-2, complex in the H-H stretch region (4022-4078 cm(-1)) by monitoring Mn+ photodissociation products. The band center of Mn+-H-2, the H-H stretch transition, is shifted by -111.8 cm(-1) from the transition of the free H-2 molecule. The spectroscopic data suguest that the Mn+-H-2 complex consists of a slightly perturbed H-2 molecule attached to the Mn+ ion in a T-shaped configuration with a vibrationally averaged intermolecular separation of 2.73 angstrom. Together with the measured Mn+center dot center dot center dot H-2 binding energy of 7.9 kJ/mol (Weis, P.; et al. J. Phys. Chem. A 1997, 101, 2809.), the spectroscopic parameters establish Mn+-H-2 as the most thoroughly characterized transition-metal cation-dihydrogen complex and a benchmark for calibrating quantum chemical calculations on noncovalent systems involving open d-shell configurations. Such systems are of possible importance for hydrogen storage applications.