| Turtle Beach Systems | business, public company | Valhalla | 1975 |
| Twentieth Century Pictures | film production company | Hollywood | June 26, 1933 |
| Twitter, Inc. | privately held company, public company | San Francisco | April 19, 2007 |
| U-Haul | car rental company, business, public company | Phoenix | 1945 |
| U.S. Bancorp | business, financial institution, credit institution, public company | Minneapolis | 1850 |
| U.S. Cellular | business, enterprise, public company | Chicago | 1983 |
| U.S. Steel | business, enterprise, public company | Pittsburgh | 2001 |
| Ubiquiti | business, enterprise, public company | New York City | October 2003 |
| UGG | business | Goleta | 1978 |
| UiPath | company, public company | New York City | 2005 |
| Ulta Beauty | business, retail chain, public company | Bolingbrook | 1990 |
| Ultimate Fighting Championship | mixed martial arts organization, enterprise | Nevada, Las Vegas | 1993 |
| Union Carbide | business, enterprise | Danbury | 1957 |
| Union Iron Works | business | San Francisco | 1849 |
| Union Pacific Railroad | railway company, public company | Omaha | 1862 |
| United Airlines | holding company, airline, public company | Chicago, Willis Tower | April 6, 1926 |
| United Artists | film production company, company | Culver City | February 5, 1919 |
| United Express | brand, airline | Chicago | 1985 |
| United Launch Alliance | launch service provider, privately held company | Centennial | December 1, 2006 |
| United Press International | news agency, organization, business, enterprise | Washington, D.C. | 1907 |
| United Space Alliance | business, enterprise | Houston | August 1995 |
| United States Army Command and General Staff College | staff college | Fort Leavenworth | 1881 |
| United States Army War College | Direct Reporting Unit, staff college, military school | — | 1901 |
| United States Centers for Disease Control and Prevention | United States federal agency, open-access publisher | Atlanta | — |
| United States Coast Guard Academy | military school, public educational institution of the United States, coast guard academy, military academy | New London | 1876 |
| United States Government Publishing Office | legislative branch agency, state publisher | — | 1861 |
| United States Information Agency | defunct government institution, civil service, information ministry, independent agency of the United States government, photo agency | Washington, D.C. | August 1953 |
| United States Merchant Marine Academy | naval academy, public educational institution of the United States | — | 1943 |
| United States Military Academy | Direct Reporting Unit, public educational institution of the United States, military museum, military academy | — | March 16, 1802 |
| United States Playing Card Company | publishing house, business | Erlanger | 1867 |
| United States Rubber Company | business | Naugatuck | 1892 |
| United States Wrestling Association | business | Memphis | 1989 |
| Universal Pictures | film production company, film studio | Universal City | April 30, 1912 |
| Universal Studios Hollywood | theme park | — | 1964 |
| University of Alabama | public educational institution of the United States, public university | Tuscaloosa | 1831 |
| University of Alabama in Huntsville | public educational institution of the United States, university | — | 1950 |
| University of Alaska Southeast | public educational institution of the United States, university | — | 1972 |
| University of Alaska System | state university system | Fairbanks | 1917 |
| University of Arkansas | public educational institution of the United States, land-grant university, public research university | Fayetteville | 1871 |
| University of Austin | private not-for-profit educational institution, university | — | — |
| University of California | state university system, land-grant university | Oakland | 1868 |
| University of California College of the Law, San Francisco | law school, public educational institution of the United States, university, academic publisher | — | 1878 |
| University of California, Berkeley | United Nations Depository Library, public educational institution of the United States, land-grant university, public research university | Berkeley | March 23, 1868 |
| University of California, Berkeley School of Law | law school | — | 1894 |
| University of California, Los Angeles | public educational institution of the United States, public research university | Los Angeles | May 23, 1919 |
| University of California, Merced | public educational institution of the United States, doctoral university: higher research activity, university, census-designated place in the United States | — | 2002 |
| University of California, Santa Cruz | educational institution, university | — | 1965 |
| University of Central Arkansas | public educational institution of the United States, university | — | 1907 |