Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula (CH3)2SO. It can uniquely provide solubility to certain very polar small molecules, such as simple biomolecules with multiple protic functional groups.

DMSO is generally used as a solvent. It can be used as a topical application to reduce acute swelling due to trauma. It is a natural product from trees that relieves muscle and joint pain, treats bladder inflammation and protects healthy cells from cancer and chemotherapy drugs.