A hinge for a folding bicycle comprising: - a first tubular portion; - a second tubular portion mounted pivoting relative to the first tubular portion around a first pivoting axis (X 1), the second tubular portion comprising a locking portion, the second the first and second tubular portions being able to assume an unfolded position in which they extend in the continuation of one another and a folded position in which they form an acute angle between them; - a blocking element having a first end portion and a second end portion, the first end portion being mounted pivoting on the first tubular portion around a second pivoting axis (X 2), the blocking element being able to assume at least one closed position in which it retains the first tubular portion and the second tubular portion in the unfolded position and an open position in which it allows the movement into the folded position of the first and second tubular portions by pivoting of the second tubular portion relative to the first tubular portion around the first pivoting axis; - a connection part having a first end portion mounted pivoting on the second end portion of the blocking element around a third pivoting axis (X 3), the connection part further having a second end portion mounted pivoting on the second tubular portion around a fourth pivoting axis (X 4); - a return device configured to bring the blocking element from its open position to its closed position; and the hinge is characterized by a locking device having a locked position in which it retains the blocking element in the closed position and an unlocked position in which it allows the blocking element to be placed in the open position, the locking device being mounted on the blocking element and comprising an engagement member configured to cooperate with the locking portion when the locking device is placed in the locked position. - a first tubular portion; - a second tubular portion mounted pivoting relative to the first tubular portion around a first pivoting axis (X 1), the second tubular portion comprising a locking portion, the second the first and second tubular portions being able to assume an unfolded position in which they extend in the continuation of one another and a folded position in which they form an acute angle between them; - a blocking element having a first end portion and a second end portion, the first end portion being mounted pivoting on the first tubular portion around a second pivoting axis (X 2), the blocking element being able to assume at least one closed position in which it retains the first tubular portion and the second tubular portion in the unfolded position and an open position in which it allows the movement into the folded position of the first and second tubular portions by pivoting of the second tubular portion relative to the first tubular portion around the first pivoting axis; - a connection part having a first end portion mounted pivoting on the second end portion of the blocking element around a third pivoting axis (X 3), the connection part further having a second end portion mounted pivoting on the second tubular portion around a fourth pivoting axis (X 4); - a return device configured to bring the blocking element from its open position to its closed position; and the hinge is characterized by a locking device having a locked position in which it retains the blocking element in the closed position and an unlocked position in which it allows the blocking element to be placed in the open position, the locking device being mounted on the blocking element and comprising an engagement member configured to cooperate with the locking portion when the locking device is placed in the locked position.