Provided is a ship propulsion system such that an increase in the size of a main engine can be minimized. The ship propulsion system (1) is equipped with: main generators (10A, 10B, 10C) that supplies power to the interior of a ship; a power distribution unit (11) that distributes the power of the main generators (10A, 10B, 10C); a first electric motor (21) that rotatably drives a first rotary shaft (27) with the power input through the power distribution unit (11); a main propeller (24) that rotates along with the first rotary shaft (27); a second electric motor (15) that rotatably drives a second rotary shaft (17) with the power input through the power distribution unit (11); and a stern-side propeller (16) that is disposed on the stern side of the main propeller (24) and rotates along with the second rotary shaft (17).