碳截存(Carbon sequestration，或Carbon dioxide sink)，也称作碳吸存、碳封存或碳固定，是将二氧化碳以各种形态保存起来。自然界中主要的碳截存者是海洋和植物与其他行光合作用的有机生物，借着生物机能吸收大气中的二氧化碳。在京都议定书中同意以碳截存的方式来作为碳补偿(Carbon offset)

Carbon sequestration is the process involved in carbon capture and the long-term storage of atmospheric carbon dioxide (CO
2). Carbon sequestration describes long-term storage of carbon dioxide or other forms of carbon to either mitigate or defer global warming and avoid dangerous climate change. It has been proposed as a way to slow the atmospheric and marine accumulation of greenhouse gases, which are released by burning fossil fuels.