John Calvin Portman Jr. (December 4, 1924 - December 29, 2017) was an American neofuturistic architect and real estate developer widely known for popularizing hotels and office buildings with multi-storied interior atria. Portman also had a particularly large impact on the cityscape of his hometown of Atlanta, with the Peachtree Center complex serving as downtown's business and tourism anchor from the 1970s onward. The Peachtree Center area includes Portman-designed Hyatt, Westin, and Marriott hotels. Portman's plans typically deal with primitives in the forms of symmetrical squares and circles.

Portman graduated from the Georgia Institute of Technology in 1950. His firm completed the Merchandise Mart (now AmericasMart) in downtown Atlanta in 1961. The multi-block Peachtree Center was begun in 1965 and would expand to become the main center of hotel and office space in Downtown Atlanta, taking over from the Five Points area just to the south. Portman would develop a similar multiblock complex at San Francisco's Embarcadero Center (1970s), which unlike its Atlanta counterpart, heavily emphasized pedestrian activity at street level.His signature work in China, the Shanghai Centre (1990), was the first of many major projects in China and elsewhere in Asia. The 5-star hotel inside, The Portman Ritz-Carlton, Shanghai (formerly Portman Shangri-La Hotel), was named after him.In 2009 Portman's work was featured in a major exhibition at Atlanta's High Museum of Art. Portman was a Fellow of the American Institute of Architects.