Phosphine sulfides are the pentavalent derivatives of organophosphines and are usually used as synthetic intermediates of organophosphines for their isolation as protected analogs because of the stability toward oxidation. Recently, several applications of phosphine sulfides have been disclosed as functional materials, organocatalysts, ligands, and extractants. In addition, several synthetic uses of phosphine sulfides have also developed, in which the thiophosphinyl group plays an essential role. This Highlight Review covers recent applications and syntheses of organophosphine sulfides.