交酯（英文：Lactide）指的是两分子α-羟基酸相互发生分子间酯化形成的六元环状二酯。其中一分子羟基酸的羟基－OH与另一分子羟基酸的羧基－COOH缩合脱去一分子水生成酯－C(O)O－，同时这一分子羟基酸的羧基－COOH又与另一分子羟基酸的羟基－OH缩合生成另一个酯基，因此交酯可以看作是以2,5-二氧代1,4-二恶烷为母体的一类含氧杂环化合物。

除了α-羟基酸外，其他羟基酸也可以两分子缩合生成环数更大的交酯，比如两分子γ-羟基丁酸分子间酯化时就可以生成十元的1,6-二氧杂环癸烷-2,7-二酮：

Lactide is the cyclic di-ester of lactic acid, i.e., 2-hydroxypropionic acid. Lactic acid cannot form a lactone as other hydroxy acids do because the hydroxy group is too close to the carboxylic group. Instead, lactic acid first forms a dimer, which is similar to a 5-hydroxyacid. The dimer contains a hydroxy group at a convenient distance from the carboxylic group for the formation of a lactone. Indeed, the dimer readily forms a six-membered cyclic diester known as lactide. Lactides may be prepared by heating lactic acid in the presence of an acid catalyst.