A magnetic tape cassette has in the front portion of the housing two pairs of fixed tape guide ribs protruding the same length frontwardly of the housing to define a guide path for the magnetic tape and also protruding so as to form linear front edges of a height greater than the width of the tape, the fixed tape guide ribs in at least one pair being formed adjacent to each other, with the upper and lower ends of the protruding front edges being integrally joined by bridges of the same material. The bridges are formed to have a given, constant width and a given, constant height upwardly and downwardly.