DNA修复是细胞中经常运行的一种进程。它使基因组免受损伤和突变，因此对细胞的生存是很重要的。在人的细胞中，一般的代谢活动和环境因素（如紫外线和放射线）都能造成DNA损伤，导致每个细胞每天多达1,000,000处的分子损害。这些损害给DNA分子造成结构上的破坏，由此可大大的改变细胞阅读信息和基因编码的方式，其余的损害引发在细胞基因体中的潜在有害突变，进而影响子细胞在进行有丝分裂后的存活。因此，DNA修复必须经常运作，以快速地改正DNA结构上的任何错误之处。当正常修复进程失效与细胞凋亡没有发生，则不可回复的DNA损伤可能会发生，包含了双股断裂与DNA与DNA交互链接。

DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells after it undergoes mitosis. As a consequence, the DNA repair process is constantly active as it responds to damage in the DNA structure. When normal repair processes fail, and when cellular apoptosis does not occur, irreparable DNA damage may occur, including double-strand breaks and DNA crosslinkages (interstrand crosslinks or ICLs).