The carboxylation of widely available raw materials with CO2 represents a highly desirable transformation in synthetic chemistry, enabling the streamlined synthesis of valuable carboxylic acids. While the photocatalytic carboxylation of activated unsaturated compounds with CO2 has emerged as a powerful strategy for accessing diverse carboxylated products, the direct carboxylation of unactivated alkynes with CO2 remains a formidable challenge due to the intrinsic inertness of both aliphatic alkynes and CO2. Herein, we report the first visible-light photocatalytic 1,2-dicarboxylation of unactivated alkynes with CO2, providing a versatile platform for synthesizing structurally diverse succinic acid derivatives. This method exhibits good functional group tolerance and high chemoselectivity under mild reaction conditions. Mechanistic investigations indicated that the in situ generated carbon dioxide radical anion (CO2•-) might initiate the first hydrocarboxylation of unactivated alkynes to deliver a key acrylate intermediate, which could undergo a second hydrocarboxylation process to selectively yield succinic acid derivatives. The synthetic utility of this protocol is further demonstrated by constructing bioactive molecules and CO2-based polyesters.