The VSM (Volcano and Seismic source Modelling) tool is a Fortran code used to model ground deformation detected by the most common geodetic techniques (interferometric SAR, GPS, leveling and EDM - Electro-optical Distance Measuring). VSM performs geophysical inversion modeling of ground deformation to retrieve the parameters of the causative magmatic source, or to retrieve the seismic source parameters. A magmatic source can be approximated (modeled) by a confined part of crust with a certain shape (e.g., a sphere, a sill, a dyke, a spheroid), which is inflating/deflating because of a change in the internal magma/gas pressure. Each shape generates a specific surface deformation pattern, and comparing the modeled deformation with that actually observed at the surface, it is possible to estimate the best-fit source parameters. The same applies to the seismic source, that is commonly described ad a rectangular plane with dip and strike angles. The VSM tool carries out this task by minimizing the difference between the observed and the computed displacement field, through a global optimization process.The VSM tool allows the user to choose among several geometrical sources: sphere (Mogi, 1958), spheroid (Yang et al., 1988), ellipsoid (Davis, 1986), fault (Okada, 1992), sill-like source (Fialko et al., 2001) and retrieves the best-fit source parameters. More sources can be combined. The VSM software tool is developed by INGV, in Fortran 90. The non-linear inversion core is by M. Sambridge (1999). This Research Object contains the OSX and Linux executables, documentation and input/output if a real example applied to Campi Flegrei (Italy) with InSAR and GPS data. Please refer to documentation for further information. Contact: Elisa Trasatti email@example.com.