British anatomist and physiologist who described blood coagulation and isolated a key protein in the coagulation process, fibrinogen, which he called coagulable lymph. He also investigated the structure of the lymphatic system and described red blood cells.

Hewson was trained in medicine at William Hunter's anatomy school in London (1759–61) and at Edinburgh (1761–62). He then returned to Hunter's school as a partner, but after a dispute with Hunter over the priority of his discoveries, he left in 1772 to establish his own school. In 1770 he was elected to the Royal Society and was awarded the Copley Medal.