光学显微镜是一种利用光学透镜产生影像放大效应的显微镜。

由物体入射的光被至少两个光学系统（物镜和目镜）放大。首先物镜产生一个被放大实像，人眼通过作用相当于放大镜的目镜观察这个已经被放大了的实像。一般的光学显微镜有多个可以替换的物镜，这样观察者可以按需要更换放大倍数。这些物镜一般被安置在一个可以转动的物镜盘上，转动物镜盘就可以使不同的目镜方便地进入光路，物镜盘的英文是Nosepiece，又译作鼻轮。

十八世纪，光学显微镜的放大倍率已经提高到了1000倍，使人们能用眼睛看清微生物体的形态、大小和一些内部结构。直到物理学家发现了放大倍率与分辨率之间的规律，人们才知道光学显微镜的分辨率是有极限的，分辨率的这一极限限制了放大倍率的无限提高，1600倍成了光学显微镜放大倍率的最高极限，使得形态学的应用在许多领域受到了很大限制。

The optical microscope, often referred to as light microscope, is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly invented in their present compound form in the 17th century. Basic optical microscopes can be very simple, although there are many complex designs which aim to improve resolution and sample contrast.