To provide a fuel injection system and an internal combustion engine which can improve combustion stability by forming an optimal fuel spray form in accordance with operating conditions of the internal combustion engine.

A fuel passage 53 is provided in a housing 41, and a suck part 44 and three injection ports 45, 46, 47, all of which are connected to the fuel passage 53, are formed at the tip of the housing 41. Then a needle valve 48 is movably supported by the housing 41, so that opening and closing of the fuel passage 53 is made possible. The three injection ports 45, 46, 47 are formed in a fan-like shape with a wide angle in the up-and-down directions, and are formed side by side in the right-and-left directions. The fuel spraying contraction rate of the second injection port 46 located in the center is set larger than that of the first and the third injection ports 45, 47 which are located on both sides.