John Wallis (1616-1703) was an English mathematician and a key figure in the development of calculus. He is best known for his work in algebra and for introducing the concept of the infinite series. Wallis also contributed to the field of number theory and was one of the first to use the symbol for infinity (∞) in his writings. In addition to his mathematical achievements, Wallis was a prominent member of the Royal Society and served as the Gresham Professor of Geometry in London. His influence extended to the education of future mathematicians, and he played a significant role in the advancement of mathematical notation and theory during the 17th century.