放大镜（Magnifying glass）是用以放大物体的凸透镜，显微镜的雏形。

放大透镜的历史可追溯至古埃及，约西元前五世纪，以埃及的象形文本表示「一片玻璃透镜」。最早的文本记载则可追溯到古罗马，约公元前一世纪，罗马皇帝尼禄的导师塞内卡写道「无论多小或模糊的文本，透过球体或注满水的玻璃壶就会放大」。亦有一说尼录皇帝曾以一个祖母绿宝石当做凸透镜来观赏斗士比赛。

早于千多年前，人们已把透明水晶或宝石磨成「透镜」，这些透镜可放大影像。

A loupe (/ˈluːp/ LOOP) is a simple, small magnification device used to see small details more closely. Unlike a magnifying glass, a loupe does not have an attached handle, and its focusing lens(es) are contained in an opaque cylinder or cone or fold into an enclosing housing that protects the lenses when not in use. Loupes are also called hand lenses.