Arnold Orville Beckman (April 10, 1900 – May 18, 2004) was an American chemist, inventor, investor, and philanthropist. While a professor at California Institute of Technology, he founded Beckman Instruments based on his 1934 invention of the pH meter, a device for measuring acidity (and alkalinity), later considered to have "revolutionized the study of chemistry and biology". He also developed the DU spectrophotometer, "probably the most important instrument ever developed towards the advancement of bioscience". Beckman funded the Shockley Semiconductor Laboratory, the first silicon transistor company in California, thus giving rise to Silicon Valley. In 1965, he retired as president of Beckman Instruments, instead becoming the chairman of its board of directors. On November 23, 1981, he agreed to sell the company, which was then merged with SmithKline to form SmithKline Beckman. After retirement, he and his wife Mabel (1900–1989) were numbered among the top philanthropists in the United States.

Beckman was born in Cullom, Illinois, a village of about 500 people in a farming community. He was the youngest son of George Beckman, a blacksmith, and his second wife Elizabeth Ellen Jewkes. He was curious about the world from an early age. When he was nine, Beckman found an 1868 chemistry textbook, Joel Dorman Steele's Fourteen Weeks in Chemistry, and began trying out the experiments. His father encouraged his scientific interests by letting him convert a toolshed into a laboratory.

Beckman's mother, Elizabeth, died of diabetes in 1912. Beckman's father sold his blacksmith shop, and became a travelling salesman for blacksmithing tools and materials. A housekeeper, Hattie Lange, was engaged to look after the Beckman children. Arnold Beckman earned money as a "practice pianist" with a local band, and as an "official cream tester" running a centrifuge for a local store.

In 1914, the Beckman family moved to Normal, located just north of Bloomington, Illinois, so that the young Beckmans could attend University High School in Normal, a "laboratory school" associated with Illinois State University. In 1915 they moved to Bloomington itself, but continued to attend University High, where Arnold Beckman obtained permission to take university level classes from professor of chemistry Howard W. Adams. While still in high school, Arnold started his own business, "Bloomington Research Laboratories", doing analytic chemistry for the local gas company. He also performed at night as a movie-house pianist, and played with local dance bands. He graduated valedictorian of his class, with an average of 89.41 over four years, the highest attained.

Beckman was allowed to leave school a few months early to contribute to the First World War effort in early 1918 by working as a chemist. At Keystone Steel and Iron he took samples of molten iron and tested them to see if the chemical composition of carbon, sulfur, manganese and phosphorus was suitable for pouring steel.

When Beckman turned 18 in August 1918, he enlisted in the United States Marines. After three months at marine boot camp on Parris Island, South Carolina, he was sent to the Brooklyn Navy Yard, for transit to the war in Europe. Because of a train delay, another unit embarked in place of Beckman's unit. Then, counted into groups in the barracks, Beckman missed being sent to Russia by one space in line. Instead, Arnold spent Thanksgiving at the local YMCA, where he met 17-year-old Mabel Stone Meinzer, who was helping to serve the meal. Mabel would become his wife. A few days later, the armistice was signed, ending the war.

Beckman attended the University of Illinois Urbana–Champaign beginning in the fall of 1918. During his freshman year, he worked with Carl Shipp Marvel on the synthesis of organic mercury compounds, but both men became ill from exposure to toxic mercury. As a result, Beckman changed his major from organic chemistry to physical chemistry, where he worked with Worth Rodebush, T. A. White, and Gerhard Dietrichson. He earned his bachelor's degree in chemical engineering in 1922 and his master's degree in physical chemistry in 1923. For his master's degree he studied the thermodynamics of aqueous ammonia solutions, a subject introduced to him by T. A. White.

Soon after arriving at the University of Illinois, Beckman joined the Delta Upsilon fraternity. He was initiated into Zeta chapter of Alpha Chi Sigma, the chemistry fraternity, in 1921 and the Gamma Alpha Graduate Scientific Fraternity in December 1922.^{[citation needed]}