| IBM Cloud Video | website, business, online video platform, online community | San Francisco | 2007 |
| Icahn School of Medicine at Mount Sinai | private not-for-profit educational institution, medical school | — | 1963 |
| Idaho State University | public educational institution of the United States, public research university | — | 1901 |
| IESE Business School | business school | — | 1958 |
| IFixit | wiki, business | San Luis Obispo | 2003 |
| IGN | online newspaper, online film database, business, video game news website | San Francisco | September 29, 1996 |
| IHeartRadio | dot-com company, internet radio, podcast directory | 32 Avenue of the Americas | — |
| IIT Institute of Design | graduate school, design school, higher education institution, academic institution | — | 1937 |
| Illinois Institute of Technology | private not-for-profit educational institution, university | Chicago | 1940 |
| Illinois Tool Works | business, public company | Glenview | 1912 |
| ImageShack | website, business | Los Gatos | November 2003 |
| Imagic | video game publisher, video game developer | Los Gatos | 1981 |
| Imagine Entertainment | television production company, film production company | Beverly Hills | November 1985 |
| IMG | business | New York City | 1960 |
| IMG Models | modeling agency, division | New York | 1987 |
| Imgur | image hosting service, website, business | San Francisco | 2009 |
| Impossible Foods | business | Redwood City | 2011 |
| In-N-Out Burger | fast food restaurant chain | Irvine | 1948 |
| Incognito Entertainment | video game developer | Salt Lake City | May 1999 |
| Incyte | business, enterprise, public company | Wilmington | 2001 |
| Indeed | review site, search engine, business, employment website | Austin | November 2004 |
| Independent Moving Pictures | film studio, organization | New York City | 1909 |
| 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 |
| Indiana University – Purdue University Indianapolis | public educational institution of the United States, university, open-access publisher | Indianapolis | 1969 |
| InFocus | business | Tigard | 1986 |
| Infor Global Solutions | software company, business | New York City | 2002 |
| 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 |