琥珀酸（IUPAC中文名称为丁二酸；传统认为它是琥珀的精髓）是一种二羧酸，化学式为HOOC–CH₂–CH₂–COOH。

在常温的情况下，纯琥珀酸是固体，呈无色无味的晶体。它的熔点及沸点分别是185°C及235°C。它形成的阴离子称为琥珀酸根离子，是三羧酸循环其中的一分子，且是能够在以下化学反应中放出电子予电子传递链：

这个过程由琥珀酸脱氢酶（或是由粒线体电子传递链中的复合物II）所催化。该复合物是4亚单位膜结合脂蛋白，配合琥珀酸的氧化作用及泛醌的还原作用。中介电子载体为黄素腺嘌呤二核苷酸及3个B亚单位Fe₂S₂群集部份。

Succinic acid (/səkˈsɪnᵻk/) is a dicarboxylic acid with chemical formula (CH₂)₂(CO₂H)₂. It is a white, odorless solid. In an aqueous solution, it ionizes to anions (that is, conjugates to a conjugate base) called succinate (/ˈsʌksᵻneɪt/), which plays a role in the citric acid cycle, an energy-yielding process in all living organisms. As a radical group it is called a succinyl (/ˈsʌksᵻnəl/) group. The name derives from Latin succinum, meaning amber, from which the acid may be obtained.