The James R. Thompson Center (JRTC; being redeveloped as Google Center and originally the State of Illinois Center) is a postmodern-style building at 100 W. Randolph Street in the Loop district of Chicago, Illinois, United States. Designed by architect Helmut Jahn around a post-modernist rotunda, it was built to house offices of the Illinois state government in Chicago. The building occupies an entire block bounded by Randolph, Lake, Clark and LaSalle streets.

Prior to the development of the State of Illinois Center, many offices of the government of Illinois were housed at 160 North LaSalle Street. Governor James R. Thompson allocated funding for the State of Illinois Center in 1978, and Jahn was selected as the architect, announcing his plans in 1980. The building opened in 1985 after several delays and a construction accident that killed five people. It was renamed for Thompson in 1993. By the 2000s, the building was functionally outdated, prompting three successive governors to propose redeveloping or selling the building. The sale proposals elicited numerous objections from preservationists, who unsuccessfully tried to have it added to the National Register of Historic Places. Alphabet Inc., the parent company of Google, finally acquired the building in 2022 and began renovating it in 2024.

The 17-story building curves and slopes facing a plaza on the southeast corner of the property. The facade is made of glass, which was originally multicolored and single-paned; the panels were replaced with insulated glass during the 2020s. On the building's roof is a round sloped skylight, which covers the building's circular atrium. A large transparent glass extension running from the skylight down the sloped front of the building, allowed views of the surrounding skyscrapers from the rotunda. The Thompson Center's atrium overlooks all of the building's stories and originally had semi-circular balconies, with exposed stairs on three sides opposite the front, and a glass enclosed elevator column opposite the front. Office floors stretched back from the balconies to the end of the building, which extended in straight outline to the back corner property lines. The building included 19 specially commissioned artworks funded by the State of Illinois Art-in-Architecture Program, among them the Monument with Standing Beast sculpture by Jean Dubuffet. The building's unconventional design has attracted mixed reviews over the years.

The James R. Thompson Center occupies the entire block bounded by Randolph, Lake, Clark and LaSalle Streets, within the Chicago Loop in downtown Chicago, Illinois, United States. The location was previously the site of the Sherman House Hotel operated by Ernie Byfield. The hotel closed in 1973 and was demolished in 1980.

The Chicago "L"'s Clark/Lake station is housed between the Thompson Center and the 203 N. LaSalle building across the street. The building serves as the main entrance to the station, which is served by the Orange, Green, Blue, Pink, Purple and Brown lines, and it leads directly to the eastern end of the station. The building is linked to the Chicago Pedway, with pedestrian tunnels connecting to 203 North LaSalle Street, the Chicago Title and Trust Company, and the City Hall-County Building. When the Thompson Center was built, it was surrounded by taller skyscrapers. The Thompson Center's architecture contrasted with that of nearby buildings, which tended to be rectangular and made of stone.

Prior to the development of the State of Illinois Center, many offices of the government of Illinois were housed at 160 North LaSalle Street. That building was insufficient for the state government's needs, so the state also had to rent space in numerous buildings, paying about $2 million a year.

Governor Dan Walker initially wanted to build a replacement building on the south end of the Loop. When Walker lost re-nomination in 1976, the developer Arthur Rubloff, one supporter of Thompson (who was ultimately elected in that election), suggested constructing the building at the north end of the Loop instead. After studying various sites for 27 months, a state agency selected the Sherman House site on March 29, 1978. That August, Thompson signed a bill to allocate $15 million for a new state-government office building on the site of the Sherman House. This move followed a failed attempt earlier that year by the Illinois General Assembly, the state's legislature, to allocate $11 million for the project; the legislature had provided only $2.5 million. At the time, Thompson considered the old LaSalle Street building to be very energy-efficient. Another $12 million for the State of Illinois Center's development was allocated in August 1979.

The building was initially expected to cost $85 million. Local architect Helmut Jahn was hired to design the State of Illinois Center, beating out seven other architects. Jahn called the project a great opportunity, saying that the limited number of stakeholders and the building's full block site gave him a large amount of flexibility with the design. In particular, the fact that the building's sole tenant was the Illinois government meant that they were "less likely to have their egos involved in a project the way [a private] owner is", according to Jahn. He presented three proposals to Thompson in 1979; two proposals were for more typical designs, while the other had an unusual curved, inclined facade. Thompson decided to go with the less conventional design, saying it "had presence" and signified a forward-looking mentality.