| Nomura Securities Co Ltd | stock exchange, business, enterprise | Nihonbashi, Tokyo | May 7, 2001 |
| Norfolk Southern Railway | railway company, business, public company | Norfolk | 1894 |
| North American Airlines | airline | Peachtree City | 1989 |
| North Carolina Agricultural and Technical State University | historically black college or university, public educational institution of the United States, land-grant university, public university | Greensboro | 1891 |
| North Carolina Central University | historically black college or university, public educational institution of the United States, university | Durham | 1909 |
| North Carolina State University | public educational institution of the United States, open-access publisher, land-grant university, public research university | Raleigh | 1887 |
| North Dakota State University | research university, public educational institution of the United States, land-grant university, public university | — | 1890 |
| North Miami Museum of Contemporary Art | art gallery, art museum | North Miami Beach | 1981 |
| Northeastern Illinois University | public educational institution of the United States, university | — | 1867 |
| Northern Air Cargo | airline | Anchorage | 1956 |
| Northern Arizona University | public educational institution of the United States, open-access publisher, public research university | — | 1899 |
| Northern Michigan University | public educational institution of the United States, public university | — | 1899 |
| Northern Pacific Railway | transcontinental railroad, railway company, business, transport company | Saint Paul | July 2, 1864 |
| Northern Trust | business, financial institution, enterprise, credit institution, public company | Illinois, Chicago | 1889 |
| Northrop | business, aerospace manufacturer | Hawthorne | 1939 |
| Northrop Grumman Corporation | defense contractor, public company, aerospace manufacturer | Falls Church | 1994 |
| Northwest Airlines | airline | Eagan | 1926 |
| Northwestern Mutual | business | Milwaukee | 1857 |
| Northwestern University | private not-for-profit educational institution, research institute, private university | Evanston | 1851 |
| Norwegian Cruise Line | business, enterprise, public company, cruise line | Miami-Dade County | 1966 |
| Nova Southeastern University | private not-for-profit educational institution, university, open-access publisher | Davie | 1964 |
| NovaLogic | video game developer | Agoura Hills | 1985 |
| NPR | radio network, public broadcaster, online newspaper without paywall, nonprofit organization, nonprofit corporation | Washington, D.C. | February 26, 1970 |
| NStigate Games | video game developer | Marin County | March 1998 |
| Nutanix | business, enterprise, public company | San Jose | 2009 |
| Nvidia | business, public company | Santa Clara | April 5, 1993 |
| NXIVM | cult, corporation, multi-level marketing company | Albany | July 20, 1998 |
| NYSE Euronext Liffe | stock exchange, stock market, business, enterprise, public company | New York Stock Exchange Building, London | April 4, 2007 |
| Oberheim Electronics | business | Oakland | 1969 |
| Oberlin College | liberal arts college, college, private not-for-profit educational institution, school, private university | Oberlin | 1833 |
| Obsidian Entertainment | video game publisher, video game developer, business | Irvine | June 12, 2003 |
| Occidental Petroleum | business, public company | Houston | 1920 |
| OceanGate, Inc. | business | Everett | 2009 |
| Oddworld Inhabitants | video game developer | Berkeley | 1994 |
| Odyssey Marine Exploration | business, public company | — | 1994 |
| OfficeMax | business, retail chain | — | 1988 |
| Ogilvy | public relations agency, advertising agency | New York City | 1948 |
| Ohio University | public educational institution of the United States, public university | Athens | 1804 |
| Ohio Valley Wrestling | business, enterprise, professional wrestling promotion | Louisville | 1997 |
| Ohio Wesleyan University | liberal arts college, Colleges That Change Lives, private not-for-profit educational institution | Delaware | 1842 |
| Oklahoma State University | public educational institution of the United States, land-grant university, public research university, sun grant institution | — | 1890 |
| Old Dominion University | sea grant institution, public educational institution of the United States, university | — | 1930 |
| Olive Garden | restaurant chain | Orlando | December 13, 1982 |
| Omega Aerial Refueling Services | airline | — | 2001 |
| Omnicom Group | advertising agency, business, public company | New York City | 1986 |
| One America News Network | news website, television channel, organization, subscription television, cable news in the United States | San Diego | July 4, 2013 |
| One Race Films | enterprise | Studio City | 1995 |
| Onsemi | business, enterprise, public company | Scottsdale | June 18, 1992 |