Hugo Paul Friedrich Schulz (August 6, 1853 – July 13, 1932) was a German pharmacologist from Wesel, Rhenish Prussia.
He studied medicine in the universities of Heidelberg and Bonn, where he did scientific work in the physiological institute of Eduard Friedrich Wilhelm Pflüger (1829-1910). In 1877 he earned his doctorate, and afterwards worked in the pharmacological institute of Karl Binz (1832-1913) at Bonn. In 1883 he was appointed professor of pharmacology at the University of Greifswald.
Schulz is known for his research of a phenomenon known as hormesis, showing that toxins can have the opposite effect in small doses than in large doses. This he demonstrated in experiments using chemical compounds on yeast cells. From his research came the "Arndt-Schulz rule", a law concerning dosages in toxicology; named along with Dr. Rudolf Arndt (1835-1900).
Schultz published a number of works in the field of pharmacology, including the well-regarded Pharmakotherapie (1898), a treatise that was included in Albert Eulenburg's Handbuch der allgemeinen Therapie und der therapeutischen Methodik.