Mary Engle Pennington (October 8, 1872 – December 27, 1952) was an American bacteriological chemist, food scientist and refrigeration engineer.

She was a fellow in physiological chemistry at Yale University from 1897 to 1899, and conducted research with Lafayette Mendel and Russell Henry Chittenden.

She educated farmers on the handling of raw milk in order to improve the safety of ice cream sold at local schools.

[5] In the same year, she accepted a position with the Women's Medical College of Pennsylvania as director of their clinical laboratory.

She also served as a research worker in the department of hygiene at the University of Pennsylvania from 1898 to 1901, and was a bacteriologist with the Philadelphia Bureau of Health.

During her time with the laboratory, Pennington and Howard Castner Pierce were awarded a U.S. patent for an all-metal poultry-cooling rack for the cooling and grading of poultry, rabbits, and game.

[10] In 1919, Pennington accepted a position with a private firm, American Balsa, which manufactured insulation for refrigeration units.

[6] In 1913 Pennington and Howard Castner Pierce were issued a U.S. patent for an all-metal poultry-cooling rack for the cooling and grading of poultry, rabbits, and game.

[17][18] Pennington died on December 27, 1952,[8] in New York, and was interred at Laurel Hill Cemetery in Philadelphia, Pennsylvania.