Lithium-ion batteries (LIBs) are considered a pivotal enabling technology for the advancement of transportation electrification, the development of stationary energy storage systems, and the integration of renewable energy sources. Despite continuous advances in energy density and cell design, the fast-charging capability of LIBs is still significantly constrained by temperature-dependent electrochemical and thermal processes, which are crucial to the overall performance of the battery. The objective is to quantify the temperature-dependent fast-charging potential and charging power capability. This is achieved by experimentally analyzing the internal resistance (IR) during the charging of three large-format prismatic state-of-the-art cells, in addition to extrapolating their charging power capability and constant-current constant-voltage charging behavior under varying thermal boundary conditions. Utilizing the IRs ascertained during the charging process, the fast-charging potential (FCP) is introduced as a dimensionless metric that expresses the temperature-induced increase in the maximum theoretically achievable charging current at a given SoC, relative to 25 °C. Elevated cell temperatures are found to reduce IR and thus increase the theoretically achievable charging power, with the FCP nearly independent of SoC but cell-specific, ranging from about 18% (CATL) to 40% (SVolt) for a temperature increase from 25 °C to 45 °C. This potential can be exploited in two ways: firstly, by increasing the C-rate while maintaining the same constant-current duration; and secondly, by extending the constant-current phase at a constant initial C-rate. The proposed methodology facilitates a systematic and comparative evaluation of the maximum theoretically attainable temperature-dependent fast-charging potential of LIBs. It provides a foundation for the development of thermally optimized fast-charging strategies.