Provided is a trigger guard for an AR15-type firearm lower receiver, attachable and removable without application of impact force. It includes an elongated trigger guard member having forward and rear ends with a rear transverse opening positioned to align with mounting openings on the receiver. A mounting pin has a size no greater in cross-section than that of the mounting openings on the receiver and a spring engagement means thereon. A deflectable spring means is operably positioned in the transverse opening to be deflected when the pin is inserted in the transverse opening and to engage the spring engagement means on the mounting pin when the mounting pin reaches a preselected position.