| Image Comics | comics publishing company, book publisher | Berkeley | 1992 |
| ImageMovers | film production company | Novato | 1997 |
| Imagic | video game publisher, video game developer | Los Gatos | 1981 |
| Imagine Entertainment | television production company, film production company | Beverly Hills | November 1985 |
| IMG Models | modeling agency, division | New York | 1987 |
| Imgur | image hosting service, website, business | San Francisco | 2009 |
| Immediate Music | record label, business | Santa Monica | 1993 |
| In-N-Out Burger | fast food restaurant chain | Irvine | 1948 |
| In-Q-Tel | nonprofit organization, business | Arlington County | 1999 |
| Incognito Entertainment | video game developer | Salt Lake City | May 1999 |
| Independent Moving Pictures | film studio, organization | New York City | 1909 |
| Indian Motorcycle | motorcycle manufacturer, subsidiary company, enterprise | Kings Mountain, Medina | 1901 |
| Indiana State University | public educational institution of the United States, public university | Terre Haute | 1865 |
| Indiana University Bloomington | public educational institution of the United States, public research university | Bloomington | 1820 |
| Indiana University of Pennsylvania | public educational institution of the United States, university | — | 1875 |
| Indiana University Press | open-access publisher, university press | Bloomington | 1950 |
| Indie Built | video game developer | Salt Lake City | 1983 |
| Infinity Ward | video game developer | Woodland Hills | 2002 |
| Inflection AI | business, company | Palo Alto | 2022 |
| Infocom | video game publisher, video game developer, business | Cambridge | June 22, 1979 |
| Infor Global Solutions | software company, business | New York City | 2002 |
| Ingram Micro | business, public company | Irvine | 1979 |
| Instacart | privately held company, business, public company | San Francisco | 2012 |
| Institute of Contemporary Art, Boston | art gallery, nonprofit organization, art museum | Boston | 1936 |
| Institute of Mathematical Statistics | mathematical society, publishing house, open-access publisher | — | 1935 |
| Integrated Device Technology | business, public company | San Jose | 1980 |
| Inter Island Airways | airline | Pago Pago | 1993 |
| Inter-American Development Bank | multilateral development bank | Washington, D.C. | 1959 |
| Intercontinental Exchange | stock market, business, public company | Atlanta | May 11, 2000 |
| Intermeccanica | automobile manufacturer | Vancouver | 1959 |
| International Association of Genocide Scholars | nonprofit organization, international association, open-access publisher | — | 1994 |
| International Flavors & Fragrances | organization, business, public company | New York City | 1958 |
| International Typeface Corporation | type foundry, defunct organization | New York City | 1970 |
| Interplay Entertainment | video game publisher, video game developer | Beverly Hills | October 1983 |
| Invicta Fighting Championships | mixed martial arts organization, business, enterprise | Enka | 2012 |
| Invicta Watch Group | business | Hollywood | 1837 |
| Invitrogen | business, enterprise, public company | Carlsbad | 1987 |
| Iowa State University | corporate body, public educational institution of the United States, land-grant university, public research university | Ames | 1858 |
| Iridium Communications | mobile network operator, business, enterprise, public company | McLean | 2001 |
| IRobot | business, enterprise, public company | Bedford | 1990 |
| Iron Crown Enterprises | tabletop role-playing game publisher, board game publishing company, business | Virginia | 1980 |
| Iron Galaxy Studios | video game publisher, video game developer | Chicago | 2008 |
| Iron Lore Entertainment | video game developer | Boston | October 2000 |
| Irrational Games | video game developer | Boston | 1997 |
| IShares | Product group, brand, business, public company | San Francisco | 2000 |
| Island Air (Hawaii) | airline | Honolulu | 1980 |
| Issuu | online service, website, business | Palo Alto | 2007 |
| ITT Corporation | business, enterprise, public company | Stamford | 1920 |