| Association for Computing Machinery | regulatory college, publishing house, organization, open-access publisher, scientific society, learned society | New York City | September 15, 1947 |
| Association for the Advancement of Artificial Intelligence | regulatory college, publishing house, scientific society | Palo Alto | 1979 |
| Astronomical Society of the Pacific | organization, academic publisher | — | 1889 |
| Astrophysics Data System | bibliographic database, data library, open-access repository | — | 1992 |
| AT&T | telecommunications company, business, enterprise, public company | Dallas | October 5, 1983 |
| Atari Corporation | video game publisher, technology company, business | Sunnyvale | July 2, 1984 |
| Atari, Inc. | video game publisher, video game developer | New York City | February 1993 |
| Atari, Inc. | video game publisher | New York City | February 1993 |
| Atlas Obscura | publishing house, brand, online encyclopedia, database | Greenpoint | 2009 |
| Au Bon Pain | business | Boston | 1978 |
| Auburn Automobile | business | Auburn | 1900 |
| Augusta National Golf Club | golf course, golf club, business | — | 1930 |
| Aurora University | private not-for-profit educational institution, university | Aurora | 1893 |
| Austin Peay State University | public educational institution of the United States, university | — | 1927 |
| Autocar Company | business | Hagerstown | 1897 |
| Automatic Data Processing | software company, business, enterprise, public company, accounting software | Roseland | 1949 |
| Avalon Hill | tabletop role-playing game publisher, board game publishing company | Baltimore, Renton | 1958 |
| Avatar Press | comics publishing company, book publisher, business, enterprise | Rantoul | 1996 |
| Avid Technology | business, enterprise, public company | Burlington | 1987 |
| Avnet | business, public company | Phoenix | 1921 |
| Awty International School | school, private school | — | 1956 |
| Axios | news website, business | Arlington County | 2017 |
| Aéropostale | clothing store chain, public company | New York City | 1973 |
| Bad Dragon | business | Phoenix | June 2008 |
| Bad Robot Productions | television production company, film production company | Santa Monica | 1998 |
| Bain & Company | management consulting company | Boston | 1973 |
| Baker University | private not-for-profit educational institution, private university | — | 1858 |
| Baltimore and Ohio Railroad | railway company, business | Baltimore | 1827 |
| Bandcamp | music streaming service, digital distribution platform, online music store | Oakland | 2007 |
| Bang Bros | pornography website, pornographic film studio | Miami | 2004 |
| Bank of America | global systemically important bank, bank, business, enterprise, credit institution | Charlotte | 1784 |
| Bank of North America | bank, central bank | Philadelphia | 1781 |
| Bank of North Dakota | bank, business | Bismarck | 1919 |
| Bank One Corporation | business | Chicago | 1863 |
| Bard College | liberal arts college, private not-for-profit educational institution | — | 1860 |
| Barnard College | liberal arts college, private not-for-profit educational institution | — | 1889 |
| Barrett Firearms Manufacturing | organization, business, enterprise | Christiana | 1982 |
| Baruch College | public educational institution of the United States, university | New York City | 1919 |
| Basic Books | book publisher | New York City | 1950 |
| Baskin-Robbins | food manufacturing, business, enterprise, ice cream parlor chain | Canton | 1945 |
| Bates College | liberal arts college, private not-for-profit educational institution | — | 1855 |
| Bauer Hockey | business, public company | Exeter | 1927 |
| Bausch Health | pharmaceutical company, business, public company | Laval, Wilmington | 1960 |
| Baylor University | church college, private not-for-profit educational institution, private university | — | 1845 |
| Be Inc. | business | Menlo Park | 1990 |
| Beats Electronics | business, enterprise | Culver City | 2006 |
| Bell Telephone Company | business | — | July 9, 1877 |
| Bellator MMA | mixed martial arts organization, sports organization, business | Newport Beach | 2008 |