A portable arm support has a hanger mount that is configured to be attached to a structure, such as an automotive door panel. A support member attaches to the hanger mount in a manner so that the support member is rotatable over a range of rotation. The support member can have a convex, curved support surface upon which a user may rest their arm. The support member may rotatably self-adjust upon placement of the user's arm on the support surface. The support member can be connected to the hanger mount via a connector, which connector is attached to a lower part of the support member, but not an upper part of the support member, so as not to resist deflection of the upper part of the support member.