Millennium Park is a public park located in the Chicago Loop, a community area of the city in Illinois, operated by the Chicago Department of Cultural Affairs and managed by MB Real Estate. The park was intended to celebrate the third millennium and is a prominent civic center near the city's Lake Michigan shoreline that covers a 24.5-acre (9.9 ha) section of northwestern Grant Park. The area was previously occupied by parkland, the Illinois Central rail yards, and parking lots. The park, which is bounded by Michigan Avenue, Randolph Street, Columbus Drive and East Monroe Drive, features a variety of public art. As of 2009, Millennium Park trailed only Navy Pier as a Chicago tourist attraction and by 2017 it had become the number one tourist attraction in the Midwestern United States. In 2015, the park became the location of the city's annual Christmas tree lighting.

Planning of the park began in October 1997. Construction began in October 1998, and Millennium Park was opened in a ceremony on July 16, 2004, four years behind schedule. The three-day opening celebrations were attended by some 300,000 people and included an inaugural concert by the Grant Park Orchestra and Chorus. The park has received awards for its accessibility and green design. Millennium Park has free admission, and features the Jay Pritzker Pavilion, Cloud Gate, the Crown Fountain, the Lurie Garden, and various other attractions. The park is connected by the BP Pedestrian Bridge and the Nichols Bridgeway to other parts of Grant Park. Because the park sits atop a parking garage and the commuter rail Millennium Station, it is considered the world's largest rooftop garden.

Some observers consider Millennium Park the city's most important project since the World's Columbian Exposition of 1893. It far exceeded its originally proposed budget of $150 million. The final cost of $475 million was borne by Chicago taxpayers and private donors. The city paid $270 million; private donors paid the rest, and assumed roughly half of the financial responsibility for the cost overruns. The construction delays and cost overruns were attributed to poor planning, many design changes, and cronyism. Many critics have praised the completed park.

In 2017, Millennium Park was the top tourist destination in Chicago and in the Midwest, and placed among the top ten in the United States with 25 million annual visitors.