脱羧反应是有机化合物中的羧基（-COOH）转变为氢（-H），同时放出二氧化碳（CO₂）的反应。

常见氨基酸脱羧生成胺的生化合成反应：

柠檬酸循环中的脱羧反应：

催化脱羧反应的酶称为脱羧酶，EC编号4.1.1。

Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO₂). Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carboxylation, the addition of CO₂ to a compound. Enzymes that catalyze decarboxylations are called decarboxylases or, the more formal term, carboxy-lyases (EC number 4.1.1).