George O. Garnsey (1840–1923) was an American architect from the city of Chicago, known for his large picturesque Queen Anne style homes.

[1] Garnsey was born in Rock Island, Illinois in 1840 and was educated at a private school in New York; in 1852 his parents brought him to Chicago.

[1] After the Great Chicago Fire in 1871, Garnsey helped to redesign many of the buildings in the city and established a national reputation for theater and opera house design.

In 1923 he was commissioned by the National Bonding and Developing Company to build a new city on the site of an old US military installation on the Santa Fe Railroad in New Mexico.

In Wisconsin, Garnsey was associated with John C. Cochraine in the design of Memorial Hall (1867) at Beloit College in the Near East Side Historical District.