Henry Prentiss Armsby (September 21, 1853 – October 19, 1921) was an American agricultural chemist, animal nutritionist, and academic administrator.

[1][2] In 1877, Samuel William Johnson hired Armsby to work as a chemist at the newly formed Connecticut Agricultural Experiment Station - the first in the nation - in New Haven.

[3] Armsby worked at the Station for four years, earned his PhD from Yale in 1879, and wrote the textbook Manual of Cattle Feeding (1880), which became a staple in the field of animal nutrition.

During a speech to the Connecticut Board of Agriculture that year, he championed the civic, scientific, and economic value of the school as a venue to produce successful farmers and community leaders.

[4] In 1887, Armsby accepted the position of Director of the newly formed Agriculture Experiment Station at Pennsylvania State College.

[8] Armsby was internationally renowned for creating an animal respiration calorimeter, which increased efficiency of cattle feeding, in 1901.

He was awarded a gold medal at the Panama-Pacific International Exposition in 1915 for his model of the calorimeter he had designed at Penn State.

[1] A U.S. Department of Agriculture report called him "the foremost exponent of research in the field of animal nutrition in the country and an international authority.

[4] The couple had five sons: Charles Lewis, Ernest Harding, Sidney Prentiss, Henry Horton, and Edward McClellan, all of whom eventually graduated from Pennsylvania State University and several of whom became academicians themselves.