红点镜（red dot sight），部份型号又名反射式瞄准镜（reflex sight），亦作内红点，是一种无放大率的光学瞄具，有光亮的瞄准点（通常为一红点）。一些望远镜及内置取景器的「傻瓜相机」亦会载有红点镜。

由于红点镜中射入眼睛的光点（光射）永远与红点镜平衡，即使眼睛不在红点镜的中轴上，也能透过红点准确瞄准，可提升高速移动或身体摇晃时的射击精确度，因此被各国大量使用于军事枪械甚至战机的抬头显示器上。另外，特殊光线除了可由发光二极管生成外，亦可由自然光或极低放射性的放射物（半永久有效）提供。

A reflector sight or reflex sight is an optical device that allows the user to look through a partially reflecting glass element and see an illuminated projection of an aiming point or some other image superimposed on the field of view. These sights work on the simple optical principle that anything at the focus of a lens or curved mirror (such as an illuminated reticle) will look like it is sitting in front of the viewer at infinity. Reflector sights employ some sort of "reflector" to allow the viewer to see the infinity image and the field of view at the same time, either by bouncing the image created by lens off a slanted glass plate, or by using a mostly clear curved glass reflector that images the reticle while the viewer looks through the reflector. Since the reticle is at infinity it stays in alignment with the device the sight is attached to regardless of the viewer's eye position, removing most of the parallax and other sighting errors found in simple sighting devices.