水银中毒或称汞中毒(Mercury poisoning)，是接触汞所导致的一种中毒现象，而大部分致毒的汞化合物都是有机化合物。

在常温常压下，汞倾向和氧结合成氧化汞。若汞遭不当扰拌或弃置时，将形成微小的汞珠，大幅增加其表面积的暴露程度，而造成危险。

在高沸点的室温环境下，饱和的汞蒸气浓度是正常汞中毒水平的好几倍。随着温度上升，危险程度更增加。

借由矿物质存积和大气的累积，分水岭地形最有可能含有高含量的汞。当地表潮湿时，植物吸收该汞，而待干燥时发布。不同植物和煤矿层含有不同等级的汞含量，而蕈类也能从土壤中吸收汞。

Mercury poisoning (also known as hydrargyria or mercurialism) is a type of metal poisoning and a medical condition caused by exposure to mercury or its compounds. Mercury (chemical symbol Hg) is a heavy metal occurring in several forms. All of these, except elemental liquid mercury (for which intravenous injection of a certain volume) produce toxicity or death with less than a gram. The damage done by elemental mercury is caused by blocking blood vessels. Mercury's zero oxidation state (Hg) exists as vapor or as liquid metal, its mercurous state (Hg) exists as inorganic salts, and its mercuric state (Hg) may form either inorganic salts or organomercury compounds; the three groups vary in effects. Toxic effects include damage to the brain, kidneys and lungs. Mercury poisoning can result in several diseases, including acrodynia (pink disease), Hunter-Russell syndrome, and Minamata disease.