丁酸，又称酪酸，是化学式为CH₃CH₂CH₂-COOH的羧酸和短链饱和脂肪酸，存在于腐臭的黄油、帕马森干酪、呕吐物和腋臭中。丁酸带有难闻的气味，味先辣后甜，与乙醚类似。10ppb浓度的丁酸即可被狗嗅出，人则大于10ppm。

丁酸是脂肪酸，在动物脂肪和植物油中以丁酸酯形式存在。其甘油酯占黄油的3~4%，当黄油腐烂后，含有难闻气味的丁酸即通过水解释放出来。它是短链脂肪酸的主要一员。丁酸为弱酸，酸度与乙酸（pK_a=4.76）类似，pK_a为4.82。该相似性与它们共有的-CH₂COOH末端结构有关。丁酸密度0.96 g/cm，摩尔质量88.1051。

Butyric acid (from Greek βούτῡρον, meaning "butter"), also known under the systematic name butanoic acid, abbreviated BTA, is a carboxylic acid with the structural formula CH₃CH₂CH₂-COOH. Salts and esters of butyric acid are known as butyrates or butanoates. Butyric acid is found in milk, especially goat, sheep and buffalo milk, butter, parmesan cheese, and as a product of anaerobic fermentation (including in the colon and as body odor). It has an unpleasant smell and acrid taste, with a sweetish aftertaste similar to ether. It can be detected by mammals with good scent detection abilities such as dogs at 10 parts per billion, whereas humans can detect it in concentrations above 10 parts per million.