A female terminal fitting is provided with protection walls 16 to avoid interference of a male terminal fitting M and to guide the male terminal fitting M to a proper position even if it is obliquely inserted. A tongue 9 is provided at or on the bottom surface of a connecting portion 3 of a female terminal fitting F by being turned inwardly so as to be elastically deformable. Protection walls 16 project from side edges of an opening end of the connecting portion 3 in such a manner as to be opposed to each other. Slanting guide surfaces 17 extending away from each other at upper ends of the protection walls 16. When a male terminal fitting M that is inserted obliquely, is slid upward along the guide surfaces to be guided automatically to a proper position.