水质浊度（turbidity），水样中悬浮物质的含量亦即混浊的程度。正常之酸性环境的水质为澄清状态，中性或碱性环境水质经常出现混浊现象，来自于金属离子与氢氧根或碳酸根所形成的悬浮固体以及水体中的微生物。

浊度测定起源于杰克逊烛光度测定法，单位为JTU（Jackson turbidity unit），现今浊度分析惯用散射比浊测定法，单位为NTU（nephelometric turbidity unit）。

Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.

Fluids can contain suspended solid matter consisting of particles of many different sizes. While some suspended material will be large enough and heavy enough to settle rapidly to the bottom of the container if a liquid sample is left to stand (the settable solids), very small particles will settle only very slowly or not at all if the sample is regularly agitated or the particles are colloidal. These small solid particles cause the liquid to appear turbid.