缓冲物质指能调节溶液的pH值，使溶液的pH值在加入一定量的酸性物质或碱性物质时保持恒定或小范围变化的一种物质。有的缓冲物质显酸性，有的缓冲物质显碱性。缓冲物质在农业、食品保存与医药等方面应用广泛。

缓冲物质可以是弱碱或弱酸，通常把缓冲物质添加到水中或其他溶剂中以制成缓冲溶液，以起到缓冲作用。例如，缓释阿司匹林中含有一些缓冲物质，例如氧化镁，使药物在经过病人的胃部时不会因与胃酸作用而改变其pH使药物失效。缓冲物质的另一种应用是用于治疗胃酸过多的抗酸片，可使胃中过多胃酸得到中和。

A buffering agent is a weak acid or base used to maintain the acidity (pH) of a solution near a chosen value after the addition of another acid or base. That is, the function of a buffering agent is to prevent a rapid change in pH when acids or bases are added to the solution. Buffering agents have variable properties—some are more soluble than others; some are acidic while others are basic. As pH managers, they are important in many chemical applications, including agriculture, food processing, biochemistry, medicine and photography.