In applied mathematics, the non-uniform discrete Fourier transform (NUDFT or NDFT) of a signal is a type of Fourier transform, related to a discrete Fourier transform or discrete-time Fourier transform, but in which the input signal is not sampled at equally spaced points or frequencies (or both).

In mathematics, the discrete Fourier transform over a ring generalizes the discrete Fourier transform, of a function whose values are commonly complex numbers, over an arbitrary ring.