Unusual photophysical properties of organicinorganic hybrid perovskites have not only enabled exceptional performance in optoelectronic devices, but also led to debates on the nature of charge carriers in these materials. This study makes the rst observation of intense terahertz (THz) emission from the hybrid perovskite methylammonium lead iodide (CH3NH3PbI3) following photoexcitation, enabling an ultrafast probe of charge separation, hot-carrier transport, and carrierlattice coupling under 1-sun-equivalent illumination conditions. Using this approach, the initial charge separation/transport in the hybrid perovskites is shown to be driven by diffusion and not by surface elds or intrinsic ferroelectricity. Diffusivities of the hot and band-edge carriers along the surface normal direction are calculated by analyzing the emitted THz transients, with direct implications for hot-carrier device applications. Further- more, photogenerated carriers are found to drive coherent terahertz-frequency lattice distortions, associated with reorganizations of the lead-iodide octa- hedra as well as coupled vibrations of the organic and inorganic sublattices. This strong and coherent carrierlattice coupling is resolved on femtosecond timescales and found to be important both for resonant and far-above-gap photoexcitation. This study indicates that ultrafast lattice distortions play a key role in the initial processes associated with charge transport. Show Partial Abstract