| Ingram Micro | business, public company | Irvine | 1979 |
| InnerSloth | privately held company, video game developer, enterprise, company | Redmond | 2015 |
| InnoCentive | business, enterprise | Waltham | 2001 |
| Inovio Pharmaceuticals | business, public company | Plymouth Meeting | 1983 |
| INSEAD | business school | Fontainebleau | 1957 |
| Instacart | privately held company, business, public company | San Francisco | 2012 |
| Institute for Scientific Information | business, enterprise | Philadelphia | 1960 |
| Institute of Contemporary Art, Boston | art gallery, nonprofit organization, art museum | Boston | 1936 |
| Institute of Electrical and Electronics Engineers | engineering society, standards organization, trade association, nonprofit organization, publishing house, open-access publisher, charitable organization, professional association, learned society, academic publisher | Manhattan | January 1963 |
| Integrated Taxonomic Information System | global species database, online database, partnership, taxonomic database | — | February 27, 1996 |
| Intel | business, public company | Santa Clara | July 18, 1968 |
| Inter Island Airways | airline | Pago Pago | 1993 |
| Inter-American Development Bank | multilateral development bank | Washington, D.C. | 1959 |
| Intermeccanica | automobile manufacturer | Vancouver | 1959 |
| International Association of Genocide Scholars | nonprofit organization, international association, open-access publisher | — | 1994 |
| International Typeface Corporation | type foundry, defunct organization | New York City | 1970 |
| Intersil | business, public company | Milpitas | 1967 |
| Intetics | software company | Naples | 1995 |
| Invesco | business, enterprise, public company | Atlanta | 1935 |
| InXile entertainment | video game developer | Newport Beach | 2002 |
| IQVIA Holdings, Inc. | business, enterprise, contract research organization, public company | Danbury, Durham | 2016 |
| Iron Galaxy Studios | video game publisher, video game developer | Chicago | 2008 |
| Irrational Games | video game developer | Boston | 1997 |
| Island Air (Hawaii) | airline | Honolulu | 1980 |
| Issuu | online service, website, business | Palo Alto | 2007 |
| It's a Laugh Productions | production company | Studio City | November 3, 2003 |
| ITT Corporation | business, enterprise, public company | Stamford | 1920 |
| J. G. Brill Company | business, enterprise | Philadelphia | 1868 |
| Jack Daniel's | distillery, business, enterprise | Jack Daniel's Distillery | 1866 |
| Jacksonville State University | public educational institution of the United States, university | — | 1883 |
| Jacobs Engineering Group | business, enterprise, public company | Harwood Center | 1947 |
| Jakks Pacific | business, public company | Malibu | 1995 |
| Jamba | restaurant chain, business, public company | Frisco | 1990 |
| JanSport | brand, business | San Leandro | 1967 |
| Jasc Software | business | Eden Prairie | 1990 |
| JBL | business | Northridge | 1946 |
| Jeep | car brand, business, enterprise, automobile manufacturer | Toledo | 1941 |
| Jelly Belly | business | Fairfield | 1898 |
| Jet | brand, business, gas station chain | — | — |
| Jewish Publication Society | book publisher, publishing house | Philadelphia | June 3, 1888 |
| Jewish Telegraphic Agency | Jewish organization, news agency, bulletin | New York City | 1917 |
| Jimmy Carter Library and Museum | museum, library | — | 1986 |
| Jimmy John's | restaurant chain, business | Champaign | 1983 |
| John Carroll University | Jesuit university, private not-for-profit educational institution | — | 1886 |
| John F. Kennedy Presidential Library and Museum | museum, library | — | 1979 |
| John F. Kennedy School of Government | public policy school, graduate school, private school | Cambridge | 1936 |
| John Hancock Insurance | business | Boston | 1862 |
| Johns Hopkins School of Medicine | medical school | — | 1893 |