The accurate determination of stator leakage inductances is presently an open issue in the analysis and testing of multi-phase electric machines. Calculation methods are available, which involve complicated and often poorly precise three-dimensional (3-D) analyses. Experimental determination techniques, using measurements on the wound stator with the rotor removed, are also possible, but quite impractical, as they need to be performed during machine manufacturing or require rotor withdrawal. In this paper, a new approach is proposed to determine all the stator self-and mutual leakage inductances of a nine-phase synchronous machine based on a minimal set (a couple) of magnetostatic finite-element (FE) simulations, and on the measurements taken during no-load and short-circuit routine tests. The procedure is applied to a wound-field salient pole nine-phase synchronous generator for validation, showing good accordance with the results obtained from measurements on the machine with the rotor removed. A discussion is also proposed on the possibility to extend the presented procedure to other multiphase topologies.