This review by Rajeshwar P. Sinha and Donat-P. Häder discusses the mechanisms of UV-induced DNA damage and repair in various organisms. The depletion of the stratospheric ozone layer due to anthropogenic pollutants has increased UV-B radiation reaching the Earth's surface, leading to significant biological impacts. UV radiation induces two major types of DNA lesions: cyclobutane-pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs), which can cause cytotoxic and genotoxic effects. Cells have developed several repair mechanisms to counteract these damages, including photo-reactivation by photolyase, excision repair (base excision repair [BER] and nucleotide excision repair [NER]), mutagenic repair, dimer bypass, recombinational repair, cell-cycle checkpoints, apoptosis, and alternative repair pathways. The review also highlights the importance of these mechanisms in maintaining genetic fidelity and survival under UV stress.This review by Rajeshwar P. Sinha and Donat-P. Häder discusses the mechanisms of UV-induced DNA damage and repair in various organisms. The depletion of the stratospheric ozone layer due to anthropogenic pollutants has increased UV-B radiation reaching the Earth's surface, leading to significant biological impacts. UV radiation induces two major types of DNA lesions: cyclobutane-pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs), which can cause cytotoxic and genotoxic effects. Cells have developed several repair mechanisms to counteract these damages, including photo-reactivation by photolyase, excision repair (base excision repair [BER] and nucleotide excision repair [NER]), mutagenic repair, dimer bypass, recombinational repair, cell-cycle checkpoints, apoptosis, and alternative repair pathways. The review also highlights the importance of these mechanisms in maintaining genetic fidelity and survival under UV stress.