Memorial Union is located on the south shore of Lake Mendota on the campus of the University of Wisconsin–Madison. On the lakeshore to the north of the building is the Terrace, a popular outdoor space overlooking the lake. It has gained a reputation as one of the most beautiful student centers on a university campus.

The exterior of the main wing was designed by University Architect Arthur Peabody. Opened on October 5, 1928, the facility is operated by the Wisconsin Union, a membership organization. Porter Butts, the first director, called it a "college union" because it combines the characteristics of a student union ("student activity center" in other countries) and a student government ("students' union" in other countries) in an organization that brings together students, faculty, and members of the surrounding community.

In 1938, the Theater wing opened. It was supposed to be a mirror image of the east wing. However, the project was delayed several years due to financial issues. The final look was very different than it was supposed to.

In 1956, the cafeteria was renovated and expanded beyond the existing building envelope. Stone that was removed from the exterior wall was reused to rip-rap the lakeshore.

The cafeteria was renovated again in 1982, and again later in 2002, when it was renamed the Lakefront on Langdon.

In 2005, a referendum to build a new Union South and to renovate Memorial Union failed, but a new referendum happened again in 2006, and this time it passed. Construction began in summer of 2012 and wrapped up in September 2017. These renovations included a redesign of the Terrace, a renovation of the Wisconsin Union Theater, the addition of new restaurants and study spaces, and the addition of the 1.3-acre Alumni Park, which opened in fall of 2017, and the addition of an underground loading dock, which also serves the adjacent Red Gym and Pyle Center.

The building was added to the National Register of Historic Places on May 19, 2015.

Building improvements were performed in two phases.

Phase I lasted from 2012 to 2014, renovating the west wing. A chunk connecting the theater to the main building was demolished and rebuilt in order to allow for a new elevator and to address accessibility issues. The Hoofers area was rebuilt too, and a new hallway was built out to the lakeshore.

The Craftshop was relocated to the lower level, the Play Circle theater was rebuilt as a black box theater, a new entrance was added, a new reception area, and a new Sunset Lounge was added in front of the theater entrance. The main theater was renamed Shannon Hall.

Phase II renovated the central core and east wings and terrace, as well as converting the parking lot into Alumni Park. A new underground loading dock was built under the park, allowing direct connection to the basement kitchens and storage areas. The loading dock also was built to serve the adjacent Red Gym and Pyle Center which eliminated the above-ground loading docks. The interior renovation included the dining areas, basement kitchen, Rathskeller, Great Hall, Main Lounge, and Tripp Commons.

Most of the Union and Terrace closed in September 2015. The Rathskeller remained open until February but the serving area was closed. A temporary sandwich bar called the Subskeller was installed.

Much of the terrace reopened in May 2016 for graduation weekend, and the first floor/basement opened the following December. The remaining areas reopened in September 2017.

Outside the main building is the Memorial Union Terrace, a stone outdoor dining and recreation area on the shore of Lake Mendota. The Terrace was designed by Peabody's daughter, Charlotte. It is a popular spot among students and local residents for socializing because of the backdrop of the lake, with its view of sailboats, and the sound of live music, usually free to the public in the evening. The Wisconsin Union Directorate funds music on the Terrace four nights a week in the summer, and on the Terrace or in der Rathskeller on weekends during the school year (depending on weather).

Within the Union are rooms and artworks reflecting the local heritage. The largest is Der Rathskeller, a German-style beerhall with elaborate murals, where political debates and card or board games are common among students over a beer. Der Rathskeller directly connects the ground floor to the Terrace outside. Also on the ground floor are the Paul Bunyan Room and dining areas. Upstairs are the Beefeater Room and the Old Madison Room. The west wing of the Union houses the Wisconsin Union Theater and Wisconsin Hoofers.

The Daily Scoop sells Babcock ice cream made at the university. Peet's Coffee Shop is a privately managed operation that serves coffee and pastries. The Campus and Community Information desk acts as an information and referral resource. There is a small retail shop offers newspapers, apparel, and snacks. The Memorial Union Box Office offers ticketing for campus events as well as bus tickets for the Van Galder Bus Line. Memorial Union houses several restaurants and cafeterias. A catering department serves conferences, events for the university, and weddings of Union members, and the annual Tudor Dinners.

The Hoofers, an activity group headquartered in the Union, offer activities on Lake Mendota and other outdoor sites.

Adjacent to the Union and Terrace is the 1.3-acre Alumni Park. The park is an art gallery and museum displaying the accomplishments of Badgers throughout the 17 decades of the university. Beneath the park is an underground loading dock, which serves the Union as well as the adjacent Red Gym, Pyle Center, and Alumni House.

The building has three main wings.

The central core is the grand historical wing. The grand entrance goes right into Memorial Hall on the second floor then into the Main Lounge. The main lounge is flanked by the Hamel Browsing Library on the left and the art gallery on the right. The central core includes two grand staircases.

The first floor of the central core contains Der Rathskeller, flanked by Der Stiftskeller on the left and the serving bar on the right. Under the grand entrance is the trophy room and bathrooms. The Paul Bunyan room is located south of the west grand staircase.

On the fourth floor of the central core contains the great hall, also known as the dance hall. The great hall has a balcony above the grand entrance.

The fifth floor contains offices.

The east wing, historically known as the Commons wing, contains most of the indoor dining areas on the first floor. On the second floor is Tripp Commons, and the upper floors contain mostly meeting rooms. The hotel rooms are located on the fourth floor.

The west wing contains the theater, Wheelhouse studios, and Wisconsin Hoofers.

• 
  Hoofer Badger Sloops on Lake Mendota behind Memorial Union
• 
  View of the Terrace in 2024
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  The Wisconsin Union Theater in Streamline Moderne style
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  Memorial Union main entrance in 2024
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  Summer solstice sunset from the Terrace, 2015
• Memorial Union Terrace in Madison, Wisconsin
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  Inside the grand entrance

• Wisconsin Union website
• The Wisconsin Union—The First 75 Years (1904-79), interviews with Wisconsin Union Director Porter F. Butts
• Memorial Union in The Buildings of the University of Wisconsin
• "About Lakefront on Langdon".
• "Memorial Union Terrace".