Summary We introduce 3D Cauchy-type integrals that extend the classic theory of Cauchy integrals to 3D potential fields. In particular, we show how we are able to evaluate the gravity and gravity gradiometry responses of 3D bodies as surface integrals over arbitrary volumes that may have spatially variable densities. This entirely new method of 3D spatial-domain modeling is particularly suited to the terrain correction of airborne gravity gradiometry (AGG) data. The surface integrals are evaluated numerically on a topographically conforming grid with a resolution equal to the digital elevation model (DEM). Thus, our method directly avoids issues related to prismatic discretization of the digital elevation model, and their associated volume integration. We demonstrate this with a model study for AGG data simulated for a 1 Eö/vHz system over the Kauring test site in Western Australia.