Duane B. Simmons, MD (August 13, 1832 – February 19, 1889) was an American physician, educator and lay Christian missionary.

Along with James Curtis Hepburn he is known as one of the pioneers of modern medicine during the Bakumatsu and early Meiji Era in Japan.

In May 1859, Simmons set sail to Japan as a medical missionary with the Dutch Reformed Church.

After a few months in Japan, Simmons made a friendly separation from the mission and established his own private medical practice treating both expatriates and Japanese at his surgery and small hospital in Yokohama.

Simmons died on February 2, 1889, at his home in Mita and was buried in Aoyama Cemetery.