Richards, Theodore William (1868-1928) was an American chemist. He won the 1914 Nobel Prize in chemistry for his exact determinations of the atomic weights of chemical elements, including those used to determine virtually all other atomic weights. He was the first American chemist to be awarded the prize.

Richards was born on Jan. 31, 1868, in Germantown, Pennsylvania. He entered Haverford College at age 14 and received a bachelor's degree in chemistry in 1885. He earned a second bachelor's degree in chemistry in 1886 and a doctoral degree in chemistry in 1888, both from Harvard University. While working toward his doctorate, Richards improved the accuracy of methods to weigh atoms. In the course of his career, he and two of his former students accurately measured the atomic weights of over 50 elements.

After graduation, Richards studied for a year in Germany on a Harvard fellowship. He joined the Harvard faculty in 1891 as an instructor in analytical chemistry. He was promoted to assistant professor in 1894. That year, Richards also invented the nephelometer, a device that uses light dispersion to measure the concentration of suspended matter in a liquid.

Richards reached the rank of full professor at Harvard in 1901. From 1903 to 1911, he chaired Harvard's chemistry department. In 1912, Richards was named Erving Professor of Chemistry and director of the university's new teaching and research laboratory.

In 1913, Richards proved the existence of lead isotopes (two or more atoms of the same element that differ in atomic weight) by investigating the weight of lead from various sources. His later work included research in thermochemistry (the study of heat and chemical reactions) and electrochemistry (the study of chemical reactions that involve electricity).

Richards died on April 2, 1928, in Cambridge, Massachusetts.