| Honeywell Aerospace | Phoenix | 1936 |
| Hormel | Austin | 1891 |
| House of Blues | Los Angeles | November 26, 1992 |
| Hudson Motor Car Company | Detroit | 1909 |
| Hulu | Santa Monica | March 2007 |
| Humana | Louisville | 1961 |
| Hupmobile | Detroit | 1909 |
| Hurley International | Costa Mesa | 1998 |
| Hy-Vee | West Des Moines | 1930 |
| Hyperloop One | Los Angeles | June 2014 |
| IBM | Armonk | June 16, 1911 |
| IBM Cloud Video | San Francisco | 2007 |
| Id Software | Richardson | February 1, 1991 |
| IFixit | San Luis Obispo | 2003 |
| Illumina | San Diego | 1998 |
| Imgur | San Francisco | 2009 |
| Immediate Music | Santa Monica | 1993 |
| In-Q-Tel | Arlington County | 1999 |
| Inflection AI | Palo Alto | 2022 |
| Infocom | Cambridge | June 22, 1979 |
| Infor Global Solutions | New York City | 2002 |
| Ingram Micro | Irvine | 1979 |
| Instacart | San Francisco | 2012 |
| Integrated Device Technology | San Jose | 1980 |
| Intercontinental Exchange | Atlanta | May 11, 2000 |
| International Flavors & Fragrances | New York City | 1958 |
| Invicta Fighting Championships | Enka | 2012 |
| Invicta Watch Group | Hollywood | 1837 |
| Invitrogen | Carlsbad | 1987 |
| Iridium Communications | McLean | 2001 |
| IRobot | Bedford | 1990 |
| Iron Crown Enterprises | Virginia | 1980 |
| IShares | San Francisco | 2000 |
| Issuu | Palo Alto | 2007 |
| ITT Corporation | Stamford | 1920 |
| Jabil | St. Petersburg | 1966 |
| Jackson Guitars | Scottsdale | 1980 |
| Jacuzzi | Chino Hills | 1917 |
| Jakks Pacific | Malibu | 1995 |
| Jasc Software | Eden Prairie | 1990 |
| JBL | Northridge | 1946 |
| Jeep | Toledo | 1941 |
| Jet | — | — |
| Jim Crockett Promotions | Charlotte | 1931 |
| John Hancock Insurance | Boston | 1862 |
| JPMorgan Chase | New York City | 1968 |
| Juniper Networks | Sunnyvale | February 6, 1996 |
| K-Swiss | Westlake Village | 1966 |