A fuel supply system includes a filler neck that is provided in a filler neck body formed in a tubular shape and has a pipe connection structure. A first member is formed separately from the filler neck. A second member is formed separately from the filler neck to be different from the first member. The first member and the second member are engaged with each other. At least one of the first member and the second member includes a protective portion that is configured to cover at least part of the pipe connection structure in a state that the first member and the second member are engaged with each other and positions of the first member and the second member are fixed relative to the filler neck. This configuration suppresses damage of the pipe connection structure that is connected with the filler neck in the fuel supply system.