Dimethylsulfoniopropionate (DMSP), is an organosulfur compound with the formula (CH₃)₂S⁺CH₂CH₂COO^-. This zwitterionic metabolite can be found in marine phytoplankton, seaweeds, and some species of terrestrial and aquatic vascular plants. It functions as an osmolyte as well as several other physiological and environmental roles have also been identified. DMSP was first identified in the marine red alga Polysiphonia fastigiata by Frederick Challenger and Margaret Simpson (later Dr. Whitaker)