Electrode materials with three-dimensional (3D) mesoporous structures possess superior features, such as a shortened solid-phase lithium diffusion distance, a large pore volume, full lithium ion accessibility, and a high specific area, which can facilitate fast lithium ion transport and electron transfer between solid/electrolyte interfaces. In this work, we introduce a facile synthesis route for the preparation of a 3D nanoarchitecture of Ge coated with carbon (3D-Ge/C) via a carbothermal reduction method in an inert atmosphere. 3D-Ge/C showed excellent cyclability: almost 86.8% capacity retention, corresponding to a charge capacity of 1216 mA h g⁻¹ even after 1000 cycles at a 2C-rate. Surprisingly, the high average reversible capacity of 1122 mA h g⁻¹ was maintained at a high charge rate of 100C (160 A g⁻¹). Even at an ultrahigh charge rate of 400C (640 A g⁻¹), an average capacity of 429 mA h g⁻¹ was attained. Further, the full cell composed of a 3D-Ge/C anode and an LiCoO₂ cathode exhibited excellent rate capability and cyclability with 94.7% capacity retention over 50 cycles. 3D-Ge/C, which offers a high energy density like batteries as well as a high power density like supercapacitors, is expected to be used in a wide range of electrochemical devices.