A novel, accelerated, and parallelized Finite-Difference Time-Domain (FDTD) based radar cross section (RCS) prediction tool, MGL-FastRCS, is introduced. MGL-FastRCS has been parallelized with OpenMP and Compute Unified Device Architecture (CUDA) for high-performance computing with multiple cores and graphics processing units (GPUs). Characteristic examples using realistic complex air and surface targets are presented. The virtual tool automatically constructs a discrete wire-grid model of the structure under investigation. It is therefore also possible to compare the FDTD results against Method-of-Moments (MoM) data.