Springfield is the capital city of the U.S. state of Illinois. Its population was 114,394 at the 2020 United States census, which makes it the state's seventh-most populous city, the second-most populous outside of the Chicago metropolitan area (after Rockford), and the most populous in Central Illinois. Approximately 208,000 residents live in the Springfield metropolitan area, which consists of all of Sangamon and Menard counties. The city lies in a plain near the Sangamon River north of Lake Springfield. Springfield is the county seat of Sangamon County and is located along historic Route 66.

Springfield was settled by European-Americans in the late 1810s, around the time Illinois became a state. The most famous historic resident was Abraham Lincoln, who lived in Springfield from 1837 until 1861, when he became President of the United States. Major tourist attractions include multiple sites connected with Lincoln including the Abraham Lincoln Presidential Library and Museum, Lincoln Home, Old State Capitol, Lincoln-Herndon Law Offices, and the Lincoln Tomb. Largely on the efforts of Lincoln and other area lawmakers, as well as its central location, Springfield was made the state capital in 1839.

As the state capital, the government of Illinois is based in Springfield. Springfield's economy is dominated by government agencies and adjacent firms that work with state and county governance, in addition to healthcare and medicine. State government institutions include the Illinois General Assembly, the Illinois Supreme Court, the office of the Governor of Illinois and historic Illinois Governor's Mansion. The University of Illinois Springfield has its campus near Lake Springfield. Weather is fairly typical for middle-latitude locations, with four distinct seasons. The city has a mayor–council form of government and governs the Capital Township. Public schools in Springfield are operated by District No. 186.