Abstract: A mobile track tamping machine for tamping ballast under the successive ties of a track during the continuous advancement of the machine comprises a tamping tool carrier vertically adjustably mounted on the machine frame and rotatable about a horizontal axis with tamping tools projecting therefrom like spokes for sequential immersion in successive cribs. The tamping tool carrier is rotated in a direction opposite to the working direction of the machine at substantially the same speed as the selected forward speed of the machine by a rotary shaft having two ends rotatably supported on the frame. An assembly of eight pairs of vibratory tamping tools is mounted on an annular support of the carrier, the 16 tamping tools extending in a vertical plane adjacent a rail, radially with respect to the rotary shaft in a rest position and peripherally equidistantly with respect to the annular support.