A system and method to generate ultrashort high beam quality pulses from spatio- temporally mode-locked multimode fiber laser are described. The invention relies on engineering the intra-cavity pulse propagation in a multimode laser cavity to shape the spatial and temporal properties of the output pulses. The invention allows the generation of Kerr-induced self-beam cleaning when mode-locking is obtained. Using this invention, high power ultrashort pulses can be achieved with a Gaussian mode profile by using commercially available multimode fibers.