Theodore M. Schleier (April 20, 1832 – December 13, 1908) was a Prussian-born American photographer, inventor, and diplomat, active primarily in the southeastern United States in the latter half of the 19th century.

After immigrating to the United States from his native Prussia,[1] Schleier initially settled in New York, where he presumably learned the burgeoning photography trade.

[4] In 1859, Schleier moved to Nashville to work in the Southern Photographic Temple of Fine Arts, a studio and gallery on Deaderick Street operated by fellow Prussian immigrant Carl Giers (1828–1877).

This gallery opened to great fanfare in June 1867, with music provided by the Knoxville Brass Band, and ice cream and drinks served by prominent German-American baker Peter Kern.

[11] In 1870, Schleier was indicted for ignoring a new state law requiring photographers to obtain a license and pay an annual privilege tax.

Schleier's attorney, German immigrant and future North Knoxville mayor Louis Gratz, argued the law was unconstitutional because it discriminated against photographers living in larger cities by charging them a higher tax.

[29] Among his various reports, Schleier noted relatively low numbers of vagrants in the Netherlands due to social programs established by the government, church and private charities.

[34] Schleier partnered with rising Knoxville painter Lloyd Branson to create several "photo-crayon portraits" which were exhibited at 1875 Eastern Division Fair.

Places and buildings photographed by Schleier during the war include the railroad bridge over the Cumberland River, Morgan Park, the Tennessee State Capitol, the tomb of James K. Polk, the Planters Hotel, and the original Elm Street Methodist Church (flanked at the time by federal barracks).

[36] He also created carte de visite photographs for soldiers stationed in the city, including members of the all-German 32nd Indiana Infantry Regiment.

[41] During the 1880s, Schleier's studio sold numerous cabinet cards, a type of photograph that had largely replaced the carte de visite as the most popular form of portraiture.

Prominent individuals for whom Schleier created cabinet cards included President James Garfield, and Lakota chiefs Crow Dog, Spotted Tail and Red Cloud.