| Hurley International | Costa Mesa | 1998 |
| Hyperloop One | Los Angeles | June 2014 |
| IBM | Armonk | June 16, 1911 |
| IBM Research | — | 1945 |
| IGN | San Francisco | September 29, 1996 |
| Illinois Tool Works | Glenview | 1912 |
| Illumina | San Diego | 1998 |
| IMG | New York City | 1960 |
| Immediate Music | Santa Monica | 1993 |
| Incyte | Wilmington | 2001 |
| Indeed | Austin | November 2004 |
| Industrial Light & Magic | San Francisco, Letterman Digital Arts Center | May 1975 |
| IndyMac | Pasadena | July 16, 1985 |
| Inflection AI | Palo Alto | 2022 |
| Infocom | Cambridge | June 22, 1979 |
| Infor Global Solutions | New York City | 2002 |
| InnoCentive | Waltham | 2001 |
| Inovio Pharmaceuticals | Plymouth Meeting | 1983 |
| Institute for Scientific Information | Philadelphia | 1960 |
| Integrated Device Technology | San Jose | 1980 |
| Intel | Santa Clara | July 18, 1968 |
| Intercontinental Exchange | Atlanta | May 11, 2000 |
| International Flavors & Fragrances | New York City | 1958 |
| Interpublic Group of Companies | New York City | 1961 |
| Intuit | Mountain View | 1983 |
| Invicta Watch Group | Hollywood | 1837 |
| IRobot | Bedford | 1990 |
| IShares | San Francisco | 2000 |
| ITT Corporation | Stamford | 1920 |
| J. B. Hunt | Lowell | 1961 |
| J. C. Penney | Plano | 1902 |
| Jack Daniel's | Jack Daniel's Distillery | 1866 |
| Jackson Guitars | Scottsdale | 1980 |
| Jakks Pacific | Malibu | 1995 |
| Jamba | Frisco | 1990 |
| Jeppesen | Inverness | 1934 |
| Jet | — | — |
| Jim Crockett Promotions | Charlotte | 1931 |
| John Hancock Insurance | Boston | 1862 |
| Johnson & Johnson | New Brunswick | 1886 |
| Jones Lang LaSalle | Chicago, Aon Center | 1783 |
| Juniper Networks | Sunnyvale | February 6, 1996 |
| Juul | San Francisco | July 2017 |
| K-R-I-T Motor Car Company | Detroit | 1909 |
| Kaiser Jeep | Toledo | 1953 |
| Kaiser Permanente | Oakland | 1945 |
| Kaltura | New York, New York City | 2006 |
| Kaplan International Languages | London | 1967 |