Charles Henry Buckius Demuth (November 8, 1883 – October 23, 1935) was an American painter who specialized in watercolors and turned to oils late in his career, developing a style of painting known as Precisionism.

Throughout his career, Demuth remained deeply attached to Lancaster. The city's modest commercial and civic architecture was the subject of hundreds of his watercolors and paintings. His depictions of warehouses, factories and row houses imbue these ordinary structures (sometimes ironically) with a grandeur and glamor normally associated with cathedrals, palaces and temples. For example, his image of two Lancaster grain silos, titled My Egypt (1927), invites the viewer to compare the massive volumetric forms to pharaonic monuments like the pyramids.

Demuth either suffered an injury when he was four years old, or may have had polio or tuberculosis of the hip, leaving him with a marked limp and requiring him to use a cane. He later developed diabetes and was one of the first people in the United States to receive insulin. Demuth pronounced his surname with emphasis upon the first syllable, earning him the nickname "Deem" among close friends. 

Demuth, along with Georgia O'Keeffe and Charles Sheeler, was a major contributor to the Precisionist art movement, which began to evolve in America around 1915. Demuth's works often depicted a specific range of forms in a quasi-Cubist, sharply defined manner, a characteristic of Precisionism. Frequently occurring scenes within Demuth's works are urban and rural landscapes, often consisting of industrial features such as bridges, smoke stacks, and skyscrapers. Demuth's "Aucassin and Nicolette," which can be viewed below, is an exemplary work of Precisionist art. Notable features include the highly structured scene lacking figures, depiction of an industrial setting, and sharp linearity created by geometric figures with no hint of abstraction. Demuth's works of this nature have been perceived as ironic and pessimistic in light of their subject matter.

Demuth, a gay artist, was a regular patron at the Lafayette Baths. His sexual exploits there are the subject of watercolors, including his 1918 homoerotic self-portrait set in a Turkish bathhouse. Demuth spent most of his life in frail health. By 1920, the effects of diabetes had begun to severely drain Demuth of artistic energy. He died at his residence in Lancaster County, Pennsylvania at the age 51 of complications from diabetes. He is buried at the Lancaster Cemetery.