Washington University in St. Louis (WashU) is a private research university in St. Louis, Missouri, United States. Founded in 1853 by a group of civic leaders and named for George Washington, the university spans 355 acres across its Danforth and Medical campuses. It comprises nine schools and offers more than 150 undergraduate, 80 master's and professional, and 50 doctoral degree programs. As of 2024, Washington University enrolled 16,399 students representing all 50 U.S. states and more than 110 countries.

Established due to a concern of a lack of institutions of higher learning in the Midwest, the university held its first classes in 1854 in downtown St. Louis. In 1905, Washington University relocated to a new campus northwest of Forest Park, which allowed for expansion and new facilities to support its growing academic programs and student body. Construction of the first building, Busch Hall, began in 1900, followed by Brookings Hall, Ridgley, and Cupples. These buildings were not occupied until 1905 in order to accommodate the 1904 Summer Olympics and St. Louis World's Fair. By 1964, more than two-thirds of incoming students came from outside the St. Louis area. In 2021, the university adopted a need-blind undergraduate-admissions policy.

Washington University joined the Association of American Universities in 1923. The university received over 32,750 applications for the Class of 2028 and admitted 12 percent. It supports more than 400 undergraduate student organizations. The university's athletic teams, the Washington University Bears, compete in NCAA Division III as founding members of the University Athletic Association and as a member of the College Conference of Illinois and Wisconsin. Its mascot is the Bear, and its official colors are red and green. The Bears have won 26 NCAA Division III championships.

Governance of the university is overseen by a Board of Trustees, which ensures its alignment with educational, financial, and social objectives. As of 2024, the university is led by Chancellor Andrew D. Martin and Provost Mark D. West. The university's endowment of $12.0 billion is among the fifteen largest in the United States. The university's motto is Per veritatem vis, which translates to "Strength through truth". It is accredited by the Higher Learning Commission. Washington University has been the venue for four presidential debates and one vice-presidential debate.

As of 2024, 26 Nobel laureates, 11 Pulitzer Prize winners, 4 United States Poets Laureate, and 6 MacArthur Fellows have been affiliated with the university as faculty or alumni. A top producer of Fulbright scholars, Washington University alumni also include 17 university presidents, 21 members of the United States Congress, and 30 Rhodes Scholars.