John Isaiah Northrop, Ph.D. (12 October 1861 – 27 June 1891) was an American zoologist at Columbia University.

He was named after his father, John Isaiah Northrop, a pharmacist.

[1] On June 28, 1889, he married Alice Belle Rich,[2] at the time professor in Botany at the Hunter College.

In 1891, almost exactly two years after his marriage, Dr. Northrop was killed in a laboratory explosion at the Columbia School of Mines.

His only child, John Howard Northrop (Nobel Laureate in Chemistry, 1946), was born nine days after his father's death.