分子伴侣（英文：Chaperone，又见称为：molecular chaperone,中文又可译为侣伴蛋白。英文单词原意是指姆，即负责监管、教育年轻未婚少女的行为的老年妇女。）是一类协助细胞内分子组装和协助蛋白质折叠的蛋白质。注意，分子伴侣与伴侣素（英文：Chaperonin）的区别。后者只是分子伴侣中的一种，前者还包括热休克蛋白Hsp60和Hsp10两个家族。另外，使用ATP协助蛋白质折叠只是一部分分子伴侣的功能，分子伴侣如Asf1者，能在细胞分裂过程中提升DNA解螺旋酶的活性并且将母链的组蛋白传递到子链。

In molecular biology, molecular chaperones are proteins that assist the covalent folding or unfolding and the assembly or disassembly of other macromolecular structures. Chaperones are present when the macromolecules perform their normal biological functions and have correctly completed the processes of folding and/or assembly. The chaperones are concerned primarily with protein folding. The first protein to be called a chaperone assists the assembly of nucleosomes from folded histones and DNA and such assembly chaperones, especially in the nucleus, are concerned with the assembly of folded subunits into oligomeric structures.