Mary Locke Petermann (February 25, 1908 – December 13, 1975) was an American cellular biochemist known for her key role in the discovery and characterization of animal ribosomes, the molecular complexes that carry out protein synthesis.

[3] At Wisconsin, she performed research on the physical chemistry of proteins with John Warren Williams and Alwin M. Pappenheimer, including analysis of antibody-antigen interactions, in particular those between diphtheria toxin and antitoxin.

[3] She received the Sloan Award for cancer research in 1963 and used the prize money to travel to Europe to perform lectures and work in the laboratory of Nobel laureate Arne Tiselius.

[3] In 1966, the American Chemical Society awarded her the Garvan Medal, a national honor given to women who have made exemplary contributions to chemistry.

[9] Later, electron microscopy by Philip Siekevitz and George Palade would show that the original "microsomes" were fragments of the endoplasmic reticulum, studded with ribosomes.

[8] Petermann had been able to isolate pure ribosomes because the high centrifugation velocities she used to sediment molecules in a high-density sugar solution spun off fragments of the endoplasmic reticulum.