The striker arrives at Priestfield after being released by Israeli side Maccabi Netanya and, if international clearance is granted, will join Mark Stimson's squad for the remaining six games of the run-in.
Ba has previously had unsuccessful trials with Leeds United (twice) and Preston North End, although both clubs had far stronger squads than Gillingham's current setup.
The powerful front man has played for a number of clubs in French football, including Troyes, Nice, Montpellier and Le Mans, and has scored goals in the top flight in France.
With goals proving hard to come by, it is hoped that Ba's arrival will bolster Gillingham's attacking options, and help get the Gills back on the goal trail with half a dozen crucial matches left this season.