Ambrose Swasey (December 19, 1846 – June 15, 1937) was an American mechanical engineer, inventor, entrepreneur, manager, astronomer, and philanthropist. With Worcester R. Warner he co-founded the Warner & Swasey Company.
Swasey was born near Exeter, New Hampshire  to Nathaniel and Abigail Swasey. He apprenticed as a machinist at the Exeter Machine Works and was afterwards employed at Pratt & Whitney. As his career progressed he became a foreman in the gear-cutting section. He developed a new technique for making gear-tooth cutters. In 1880 he and Warner formed their eponymous firm, which quickly moved to Cleveland, Ohio. Swasey would perform the engineering and machine development at this company.
The close friends Warner and Swasey built their homes next to each other on Euclid Avenue in Cleveland, a street that was known as "Millionaire's Row".
In addition to army ordnance contracts, the firm of Warner & Swasey became notable for their work on astronomical observatories and equipment. The founders were interested in astronomy as an avocation, and in the field's quest for better optical telescopes, which was burgeoning at the time. They also realized that obtaining contracts to build large astronomical observatories would provide publicity for their company.
In 1885 Swasey completed work at McCormick Observatory on the 45-foot dome, which was the largest in the world, and had a unique, 3 shutter design. In 1887 Swasey built the mount for the 36-inch refracting telescope at Lick Observatory. In 1898 he manufactured a dividing engine for the U.S. Naval Observatory that was used to make the meridian circles. Both the building and dome of the Dominion Astrophysical Observatory were made by Warner and Swasey Co. Other observatory telescopes and components were built by the company at the Kenwood Observatory, Yerkes Observatory, Argentine National Observatory, the Swasey Observatory at Denison University, and the Case School of Applied Science Observatory.
Both Warner and Swasey were amateur astronomers. In 1920 they made a joint donation to the Case School of Applied Science to fund the construction of an observatory. This was named the Warner and Swasey Observatory in their honor, and the observatory was used for research by the Case astronomy department. The observatory maintained by the department today is still known by this name today.
Swasey Hall (1917, "懷士堂"), a red brick hall, is the landmark of Sun Yat-sen University, one of the top colleges in China. It was named after Swasey for his USD$25000 donation to the then university Christian YMCA society hall. Now it serves as a conference hall.
Other donations made by Swasey include the Swasey Chapel at Denison University in Granville, Ohio (1924), a bandstand in Exeter by architect Henry Bacon (1916), a library building to Colgate Rochester Divinity School and the endowment of a chair for a professor of physics at the Case School of Applied Sciences. The chimes in the chapel were included as a memorial to his wife, Lavinia Marston Swasey.