Mary Rita Cooke Greenwood (born April 11, 1943[citation needed]) is an American academic and nutritionist.

She had held leadership positions in several academic and profession societies and had served in several scientific organizations within the United States government.

She currently holds an appointment as a Distinguished Professor Emerita of Nutrition and Internal Medicine at the University of California, Davis.

In 2005, the University of California found that Dr. Greenwood had violated its conflict of interest rules related to a management position created for a colleague with whom she co-owned a rental property.

[5] The university found no evidence of improper conduct in a second allegation that she influenced a position held by her son at UC Merced, concluding no pattern of impropriety or ethics violations in regard to both matters that were thoroughly investigated.