盐度（以S表示，Salinity）是指海水内盐的含量。在陆地上，相关的主题为盐害。 盐度习惯以千分之一表示。

• 冰原或冰山形成
• 冰溶解
• 与盐度不同的水混合
• 潮汐
• 蒸发
• 雨水
• 大陆径流

Salinity is the saltiness or dissolved salt content of a body of water (see also soil salinity). Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, and is a thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water.