Olivine-structured LiMnPO₄ with 3D foldaway-lantern-like hierarchical structures have been prepared via a one-step, template-free, solvothermal approach in ethylene glycol. The foldaway-lantern-like LiMnPO₄ microstructures are composed of numerous nanoplates with thickness of about 20 nm. A series of electron microscopy characterization results indicate that the obtained primary LiMnPO₄ nanoplates are single crystalline in nature, growing along the [010] direction in the (100) plane. Time-dependent morphology evolution suggests that ethylene glycol plays dual roles in oriented growth and self-assembly of such unique structures. After carbon coating, the as-prepared LiMnPO₄ cathode demonstrated a flat potential at 4.1 V versus Li/Li⁺ with a specific capacity close to 130 mA h g⁻¹ at 0.1 C, along with excellent cycling stability.