Abstract: An arm stabilizer apparatus is attachable to a belt and includes a base assembly which includes belt connectors for connecting the base assembly to the belt. A hinge is connected to the base assembly, and an adjustable-length arm stabilizer assembly is connected to the hinge. The apparatus can be used in three modes: an in-use orientation; one non-use orientation in which the apparatus is oriented above the belt; and another non-use orientation in which the apparatus is oriented below the belt. The in-use orientation is adjustable, and the apparatus returns to an adjusted in-use orientation from a previous non-use orientation. In the in-use orientation, the apparatus is oriented in an arm-reception orientation, whereby a portion of a person's upper arm can be supported by the adjustable-length arm stabilizer assembly for aiming a weapon, such as a rifle or bow. An adjustable-length arm stabilizer assembly is pivotally connected to the hinge pin.