Abstract: A trigger lock that can be mounted to the trigger guard of a handheld firearm. The trigger lock has a cover assembly displaceably mounted to a lock housing assembly. The cover assembly is displaceable between a locked position and an unlocked position. A mount adapter is removeably mated to a housing body within the lock housing assembly. The removeable mount adapter has a mount surface shaped to correspond with the outer surface of the trigger guard, allowing the trigger lock to be used on various makes and models of firearms. The trigger lock includes a locking means which in one embodiment has a lock rotor with a camming surface to displace one or more locking members into the cover assembly.