We introduce a gravity anomaly separation method based on frequency-domain Wiener filtering. Gravity anomaly separation can be effected by such wavelength filtering when the gravity response from the geologic feature of interest (the signal) dominates one region (or spectral band) of the observed gravity field's power spectrum. The Wiener filter is preferable to a conventional band-pass filter because geologic information from the study area can be incorporated to a greater extent in specifying the filter's transfer function. Our method differs from previous Wiener filtering schemes in that it provides, through direct modeling of known geology (e.g., outcrop and borehole data), a more objective estimate of the signal power spectrum required for defining the transfer function of the filter. We illustrate the technique first with synthetic data, and then with a field example from the southern Paradox basin. The Paradox basin example reveals the limitation inherent to all wavelength filtering which results from spectral overlap between the gravity signal and the spectral contributions of other geologic sources. In the study area, significant spectral overlap occurs between the gravity effects of sources in the Precambrian basement and the gravity signal arising from the density contrast across the Mississippian-Pennsylvanian interface.