A connector including: a terminal; a housing configured to accommodate the terminal; and a retainer including a locking portion configured to lock the terminal when the terminal is accommodated in the housing; wherein the housing includes: a front housing having a terminal accommodating chamber into which the terminal is configured to be inserted and in which the terminal is to be accommodated; and a rear housing configured to be attached to the front housing from a rear side of an insertion direction in which the terminal is inserted into the terminal accommodating chamber, the rear housing including a lance configured to, when the terminal is accommodated in the terminal accommodating chamber, lock a rear portion of the terminal in the insertion direction, wherein the retainer is configured to be attached between the front housing and the rear housing and to be displaceable along a direction perpendicular to the insertion direction between a locking position and a non-locking position, and wherein the retainer moves from the non-locking position to the locking position and the locking portion locks the rear portion of the terminal in the insertion direction accommodated in the terminal accommodating chamber, characterized in that the retainer has a detection protrusion protruding from an outer peripheral surface of the rear housing in a radial direction of the connector when the retainer is at the non-locking position. a terminal; a housing configured to accommodate the terminal; and a retainer including a locking portion configured to lock the terminal when the terminal is accommodated in the housing; wherein the housing includes: a front housing having a terminal accommodating chamber into which the terminal is configured to be inserted and in which the terminal is to be accommodated; and a rear housing configured to be attached to the front housing from a rear side of an insertion direction in which the terminal is inserted into the terminal accommodating chamber, the rear housing including a lance configured to, when the terminal is accommodated in the terminal accommodating chamber, lock a rear portion of the terminal in the insertion direction, wherein the retainer is configured to be attached between the front housing and the rear housing and to be displaceable along a direction perpendicular to the insertion direction between a locking position and a non-locking position, and wherein the retainer moves from the non-locking position to the locking position and the locking portion locks the rear portion of the terminal in the insertion direction accommodated in the terminal accommodating chamber, characterized in that the retainer has a detection protrusion protruding from an outer peripheral surface of the rear housing in a radial direction of the connector when the retainer is at the non-locking position. a front housing having a terminal accommodating chamber into which the terminal is configured to be inserted and in which the terminal is to be accommodated; and a rear housing configured to be attached to the front housing from a rear side of an insertion direction in which the terminal is inserted into the terminal accommodating chamber, the rear housing including a lance configured to, when the terminal is accommodated in the terminal accommodating chamber, lock a rear portion of the terminal in the insertion direction, wherein the retainer is configured to be attached between the front housing and the rear housing and to be displaceable along a direction perpendicular to the insertion direction between a locking position and a non-locking position, and wherein the retainer moves from the non-locking position to the locking position and the locking portion locks the rear portion of the terminal in the insertion direction accommodated in the terminal accommodating chamber, characterized in that the retainer has a detection protrusion protruding from an outer peripheral surface of the rear housing in a radial direction of the connector when the retainer is at the non-locking position.