Filling unit for a manufacturing machine for the production of disposable cartridges for electronic cigarettes; the filling unit has: a cylindrical tank which is arranged horizontally, is mounted so as to rotate in a stepwise manner around a vertical rotation axis, is delimited, at the bottom, by a base disc having a circular shape, and is delimited, on the sides, by a cylindrical side wall; a feeding duct that feeds a flow of tobacco inside the tank; a plurality of groups of seats, each of which is obtained in the base disc and is adapted to receive and contain a corresponding dose of tobacco; and a transfer device which is arranged in a fixed position and cyclically transfers the doses of tobacco contained inside the seats of a group standing still.