| The McClatchy Company | Sacramento | 1857 |
| The Mosaic Company | Plymouth | 2004 |
| The Muppets Studio | Los Angeles | 2004 |
| The NPD Group | Port Washington | 1967 |
| The Onion | Chicago | 1988 |
| The Salt Lake Tribune | — | 1870 |
| The Travelers Companies | New York City | 1853 |
| The Walt Disney Company | Burbank | October 16, 1923 |
| Thermo Fisher Scientific Inc. | Waltham | 2006 |
| Thiokol | Trenton, Brigham City | 1929 |
| THX | San Rafael | 1983 |
| TIAA | New York City | 1918 |
| Tibco Software | Palo Alto | 1997 |
| Tiffany & Co. | New York City | 1837 |
| Tiger Electronics | Vernon Hills | 1978 |
| Time Inc. | New York City | November 28, 1922 |
| Time Warner Cable | New York City | 1989 |
| Timex Group USA | Middlebury, United States | 1854 |
| Titleist | Fairhaven | 1932 |
| TKO Group Holdings | New York City | September 12, 2023 |
| Tommy Hilfiger B.V. | New York City, Amsterdam | 1985 |
| Toro | Bloomington | 1914 |
| Total Nonstop Action Wrestling | Nashville | January 4, 2024 |
| Touchstone Television | California | December 4, 2014 |
| Tower Records | Sacramento | 1960 |
| Trader Joe's | Monrovia | 1958 |
| Trimark Pictures | Santa Monica | 1985 |
| Trimble | Westminster | 1978 |
| Tripadvisor | Needham | February 14, 2000 |
| Trump Steaks | New York City | May 8, 2007 |
| Trump University | New York City | 2005 |
| Tseng Labs | Pennsylvania | 1983 |
| Turner Broadcasting System | CNN Center | 1970 |
| Turnitin | Oakland | 1997 |
| Twilio | San Francisco | 2008 |
| Two Steps from Hell | Los Angeles | 2006 |
| U.S. Cellular | Chicago | 1983 |
| Uber | San Francisco | March 2009 |
| Ubiquiti | New York City | October 2003 |
| Ulta Beauty | Bolingbrook | 1990 |
| Ultimate Pro Wrestling | California | 1998 |
| Undead Labs | Seattle | November 23, 2009 |
| Under Armour | Baltimore | 1996 |
| Unimation | — | 1962 |
| Union Iron Works | San Francisco | 1849 |
| United Airlines Holdings | Chicago | December 30, 1968 |
| United Natural Foods | Providence | 1996 |
| United Space Alliance | Houston | August 1995 |