| Trump Mobile | mobile virtual network operator, brand | — | June 16, 2025 |
| Trump Steaks | business | New York City | May 8, 2007 |
| TRW Inc. | business, enterprise | Euclid | 1901 |
| Turner Broadcasting System | production company, media company, business, enterprise | CNN Center | 1970 |
| Turner Construction | business | New York City | 1902 |
| Turner Entertainment | production company, business, talent agency | United States | August 4, 1986 |
| Turtle Beach Systems | business, public company | Valhalla | 1975 |
| Twentieth Century Pictures | film production company | Hollywood | June 26, 1933 |
| Twilio | website, business, company, public company | San Francisco | 2008 |
| Tyson Foods | business, enterprise, public company | Springdale | 1935 |
| U.S. Bancorp | business, financial institution, credit institution, public company | Minneapolis | 1850 |
| U.S. Steel | business, enterprise, public company | Pittsburgh | 2001 |
| Udacity | educational institution, website, company | Mountain View | June 2011 |
| Udemy | website, education company | San Francisco | 2010 |
| UL LLC | standards organization, certification services provider, partnership | Northbrook | 1894 |
| Ultimate Fighting Championship | mixed martial arts organization, enterprise | Nevada, Las Vegas | 1993 |
| Undead Labs | business | Seattle | November 23, 2009 |
| Unimation | business | — | 1962 |
| Union Carbide | business, enterprise | Danbury | 1957 |
| Union College | private not-for-profit educational institution, private university | Schenectady | February 25, 1795 |
| 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 Airlines Holdings | business, enterprise, public company | Chicago | December 30, 1968 |
| United Fruit Company | multinational corporation, business | New Orleans | 1899 |
| United Parcel Service | business, public company | Sandy Springs | August 28, 1907 |
| United Plankton Pictures | privately held company | Burbank | April 1, 1998 |
| United Press International | news agency, organization, business, enterprise | Washington, D.C. | 1907 |
| United Space Alliance | business, enterprise | Houston | August 1995 |
| United States Air Force Academy | Field Operating Agency, air force academy | Air Force Academy | August 14, 1954 |
| United States Army Command and General Staff College | staff college | Fort Leavenworth | 1881 |
| United States Army Infantry School | military infantry school | Fort Benning | 1918 |
| 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 Military Academy | Direct Reporting Unit, public educational institution of the United States, military museum, military academy | — | March 16, 1802 |
| United States Naval Academy | naval academy, public educational institution of the United States, census-designated place in the United States, observatory | Naval Academy | 1845 |
| United States Naval Institute | institute, 501(c)(3) organization, publishing house | Annapolis | 1873 |
| United States Playing Card Company | publishing house, business | Erlanger | 1867 |
| United States Rubber Company | business | Naugatuck | 1892 |
| United States Wrestling Association | business | Memphis | 1989 |
| United Technologies Corporation | business, enterprise, public company | Hartford | 1929 |
| UnitedHealth Group | business, enterprise, public company | Minnetonka | 1977 |
| Universal Epic Universe | theme park | — | May 22, 2025 |
| Universal Music Group | record label group, major label, record company, public company | Broadway, New York, Santa Monica, California | September 1934 |
| Universal Pictures | film production company, film studio | Universal City | April 30, 1912 |
| Universal Studios Florida | theme park | — | 1990 |