Columbia is a city in Missouri, United States. It was founded in 1821 as the county seat of Boone County and had a population of 126,254 as recorded in the 2020 census, making it the fourth-most populous city in Missouri. Columbia is a Midwestern college town, home to the University of Missouri, a major research institution also known as MU or Mizzou. In addition to the university and surrounding Downtown Columbia are Stephens College and Columbia College, giving the city its educational focus and nearly 40,000 college students. It is the principal city of the Columbia metropolitan area, population 215,811, and the central city of the nine-county Columbia–Jefferson City–Moberly combined statistical area with 415,747 residents. The city is the fastest growing municipality in Missouri, with a growth of almost 40% since 2000, and a population estimated at 130,000 in 2024. Columbia is among the most-educated cities in the United States with about half of citizens being college graduates and about a quarter holding advance degrees.

The city is built on the oak-forested hills and rolling prairies of Mid-Missouri, near the Missouri River, where the Ozark Mountains transition into plains and savanna. At the city's center is the Avenue of the Columns (8th Street), connecting Francis Quadrangle and Jesse Hall to the Boone County Courthouse and the City Hall. Surrounding Columbia is a greenbelt including Rock Bridge Memorial State Park, Eagle Bluffs Conservation Area, the Mark Twain National Forest, Katy Trail State Park, Finger Lakes State Park, and the Big Muddy National Fish and Wildlife Refuge. Limestone bedrock forms bluffs and glades while rain dissolves the bedrock, creating karst (caves and springs) which water the Hinkson, Roche Perche, Flat Branch, and Bonne Femme creeks. Within city limits, there is an extensive city parks and trails system with a focus on non-motorized transportation, including the MKT Trail. The Columbia Agriculture Park is home to the nationally-regarded Columbia Farmers Market.

Originally an agricultural town, education and healthcare are now Columbia's primary economic concern, with secondary interests in the insurance, finance, and technology sectors. Companies founded in Columbia include: Carfax, Shelter Insurance, Veterans United Home Loans, MFA Incorporated, MFA Oil, Slackers CDs and Games, MidwayUSA, EquitmentShare, and Scripps News. The University of Missouri Health Care system operates six hospitals in Columbia, several clinics, and The Thompson Center for Autism and Neurodevelopment. There is also the county-owned Boone Hospital Center, several smaller private hospitals, and the Harry S. Truman Veterans' Hospital, adjacent to University Hospital and MU School of Medicine. The University of Missouri nuclear reactor is the most-powerful research reactor in the United States and the sole supplier of important radioisotopes used in nuclear medicine.

Cultural institutions include the State Historical Society of Missouri, the Museum of Art and Archaeology, the Missouri Symphony, the North Village Arts District, The Blue Note, the Missouri Theatre, The Conservatory of the Performing Arts at Stephens College, the Boone County Historical Society, Columbia Public Library, Ragtag Cinema and the annual True/False Film Festival, an internationally-known documentary festival. The Missouri Tigers, the state's only major college athletic program, play football at Faurot Field and basketball at Mizzou Arena as members of the Southeastern Conference (SEC). The city has been known as the "Athens of Missouri" for its educational emphasis and classic beauty, but is more commonly called "CoMo".