A connector comprising: a connector housing that accommodates a terminal to be connected in a fitting direction to a mating terminal accommodated in a mating connector housing; a front holder into which a part of the connector housing is inserted and that regulates movement of the terminal in a detachment direction of the fitting direction; and a locking structure that locks the front holder with respect to the connector housing, wherein the locking structure includes a locking protrusion (73, 74) provided on one of the connector housing and the front holder and formed to protrude in a first direction orthogonal to the fitting direction, at least one locking arm (55, 56) provided on the other of the connector housing and the front holder and formed to extend in the fitting direction, and at least one regulating surface (7c, 7d, 7e, 7f) provided to face the locking protrusion (73, 74) in a second direction orthogonal to the fitting direction and the first direction and regulating movement of the locking arm (55, 56) in the second direction when the locking arm (55, 56) faces the locking protrusion (73, 74) in the second direction, the locking arm (55, 56) is inserted between the locking protrusion (73, 74) and the regulating surface (7c, 7d, 7e, 7f) and in which one or more locking portions (55a, 55b, 56a, 56b) at least partly overlapping with the locking protrusion (73, 74) are formed when viewed from the fitting direction, characterized in that one of the locking arm (55, 56) and the locking protrusion (73, 74) is a deformable member that is elastically deformable in the first direction and the second direction with respect to the connector housing or the front holder provided with the one of the locking arm (55, 56) and the locking protrusion (73, 74), and the deformable member is configured to elastically deform in the first direction when the locking portion (55a, 55b, 56a, 56b) and the locking protrusion (73, 74) face each other in the second direction so that the locking portion (55a, 55b, 56a, 56b) overrides the locking protrusion (73, 74). a connector housing that accommodates a terminal to be connected in a fitting direction to a mating terminal accommodated in a mating connector housing; a front holder into which a part of the connector housing is inserted and that regulates movement of the terminal in a detachment direction of the fitting direction; and a locking structure that locks the front holder with respect to the connector housing, wherein the locking structure includes a locking protrusion (73, 74) provided on one of the connector housing and the front holder and formed to protrude in a first direction orthogonal to the fitting direction, at least one locking arm (55, 56) provided on the other of the connector housing and the front holder and formed to extend in the fitting direction, and at least one regulating surface (7c, 7d, 7e, 7f) provided to face the locking protrusion (73, 74) in a second direction orthogonal to the fitting direction and the first direction and regulating movement of the locking arm (55, 56) in the second direction when the locking arm (55, 56) faces the locking protrusion (73, 74) in the second direction, the locking arm (55, 56) is inserted between the locking protrusion (73, 74) and the regulating surface (7c, 7d, 7e, 7f) and in which one or more locking portions (55a, 55b, 56a, 56b) at least partly overlapping with the locking protrusion (73, 74) are formed when viewed from the fitting direction, characterized in that one of the locking arm (55, 56) and the locking protrusion (73, 74) is a deformable member that is elastically deformable in the first direction and the second direction with respect to the connector housing or the front holder provided with the one of the locking arm (55, 56) and the locking protrusion (73, 74), and the deformable member is configured to elastically deform in the first direction when the locking portion (55a, 55b, 56a, 56b) and the locking protrusion (73, 74) face each other in the second direction so that the locking portion (55a, 55b, 56a, 56b) overrides the locking protrusion (73, 74).