An internal-combustion engine includes a cylinder, a piston, a spark plug, and a fuel injection device. The piston includes a top surface, a guiding protrusion, and a cavity. The cavity is provided at a position closer to the fuel injection device than the guiding protrusion when viewed from above the top surface of the piston. The guiding protrusion includes a guiding surface to guide the fuel mist toward the spark plug when the fuel mist is injected from the fuel injection device at a first predetermined timing in a compression stroke. The cavity includes a guiding wall portion to guide the fuel mist toward the spark plug when the fuel mist is injected from the fuel injection device at a timing in the compression stroke between the first predetermined timing and a second predetermined timing.