Finite-difference time-domain (FDTD) is a widely used computation modelling technique that is one of the means to computationally model many scientific and engineering problems dealing with electromagnetic wave interactions and material structures.

FDTD modelling applications range from the analysis and optimization of antennas (for radio, television and radar), to the design of microwave circuits and the influence of electromagnetic fields on the human body (wireless communications devices, digital interconnects, and biomedical imaging/treatment), to visible light (photonic crystals, nanoplasmonics, and biophotonics).