Abstract: Plants play a pivotal role in the global sulfur cycle as the dominant reducer of inorganic sulfur. Inorganic sulfate in the soil is taken up by plant roots, reduced, and assimilated into cysteine, the first organic reduced sulfur, from which many critical sulfur-containing metabolites are derived and play essential roles in plant development, abiotic stress tolerance, disease and insect resistance, as well as crop yield and grain quality. Sulfur may have the most complex metabolism and regulation and serve more biological functions than any other nutrients in plants. This review summarizes the recent advances in metabolism and regulation of sulfur and its roles in stress tolerance. Important unsolved problems in sulfur metabolism and the emerging issue of sulfur