Abū Bakr Muhammad ibn Zakariyyā al-Rāzī (ابوبكر محمّد زکرياى رازى Abūbakr-e Mohammad-e Zakariyyā-ye Rāzī, also known by his Latinized name Rhazes or Rasis) (854 CE – 925 CE), was a Persian polymath, physician, alchemist, philosopher, and important figure in the history of medicine.
A comprehensive thinker, Razi made fundamental and enduring contributions to various fields, which he recorded in over 200 manuscripts, and is particularly remembered for numerous advances in medicine through his observations and discoveries. An early proponent of experimental medicine, he became a successful doctor, and served as chief physician of Baghdad and Rey hospitals. As a teacher of medicine, he attracted students of all backgrounds and interests and was said to be compassionate and devoted to the service of his patients, whether rich or poor.
According to the Encyclopaedia Britannica (1911) he was among the first to use humoral theory to distinguish one contagious disease from another, and wrote a pioneering book about smallpox and measles providing clinical characterization of the diseases. He also discovered numerous compounds and chemicals including Alcohol, kerosene, among others.
Through translation, his medical works and ideas became known among medieval European practitioners and profoundly influenced medical education in the Latin West. Some volumes of his work Al-Mansuri, namely "On Surgery" and "A General Book on Therapy", became part of the medical curriculum in Western universities. Edward Granville Browne considers him as "probably the greatest and most original of all the Muslim physicians, and one of the most prolific as an author" and has been described as a doctor's doctor, the father of pediatrics, and a pioneer of ophthalmology.