紫外－可见分光光度法（Ultraviolet–visible spectroscopy，UV-Vis），又称紫外－可见分子吸收光谱法，是以紫外线－可见光区域电磁波连续光谱作为光源照射样品，研究物质分子对光吸收的相对强度的方法。通过分子紫外－可见分子吸收光谱法的分析可以进行定性分析，并可依据朗伯-比尔定律进行定量分析。

当光的波长减小到一定数值时，溶剂对它产生强烈的吸收，即“端吸收”，样品测试就在“端吸收”的透明界限之内。

常用溶剂的透明界限如下表：

Ultraviolet–visible spectroscopy or ultraviolet-visible spectrophotometry (UV-Vis or UV/Vis) refers to absorption spectroscopy or reflectance spectroscopy in the ultraviolet-visible spectral region. This means it uses light in the visible and adjacent (near-UV and near-infrared [NIR]) ranges. The absorption or reflectance in the visible range directly affects the perceived color of the chemicals involved. In this region of the electromagnetic spectrum, molecules undergo electronic transitions. This technique is complementary to fluorescence spectroscopy, in that fluorescence deals with transitions from the excited state to the ground state, while absorption measures transitions from the ground state to the excited state.