A collapsible reflective optical sight for a firearm, including a base configured to mount the collapsible reflective optical sight to a firearm; a lens attached to and able to rotate with respect to the base, wherein the lens includes an optic with a reflective surface, and the lens is able to be folded with respect to the base to store the lens in a collapsed configuration and is able to be angled with respect to the base to aim the firearm with the lens in a deployed configuration; a light source on the base that reflects a light off the reflective surface of the optic to aim the firearm; and a mechanical sight adjustably mounted to the base to aim the firearm. Additionally, the collapsible reflective optical sight can include a firearm and a hood.