| 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 |
| Association of Universities for Research in Astronomy | consortium, open-access publisher | — | 1957 |
| AST Research | business | Irvine | 1980 |
| Astra | launch service provider, startup company, aerospace manufacturer | Alameda | 2005 |
| Astrophysics Data System | bibliographic database, data library, open-access repository | — | 1992 |
| ATA Airlines | airline | Indianapolis | 1973 |
| Atari Corporation | video game publisher, technology company, business | Sunnyvale | July 2, 1984 |
| Atari Games | video game publisher, video game developer | Milpitas | July 1984 |
| Atari, Inc. | video game publisher, video game developer | Sunnyvale | June 9, 1972 |
| 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 |
| Aurora University | private not-for-profit educational institution, university | Aurora | 1893 |
| Austin Peay State University | public educational institution of the United States, university | — | 1927 |
| Automatic Data Processing | software company, business, enterprise, public company, accounting software | Roseland | 1949 |
| AutoNation | business, car dealership, public company | Fort Lauderdale | 1996 |
| AutoZone | car parts shop chain, public company | Memphis | 1979 |
| Avalon Hill | tabletop role-playing game publisher, board game publishing company | Baltimore, Renton | 1958 |
| Ave Maria University | private not-for-profit educational institution, university | — | 1998 |
| Avery Dennison | public company | Glendale | 1935 |
| AviaBellanca Aircraft | aerospace manufacturer | Alexandria | 1927 |
| Avis Budget Group | business, public company | Parsippany-Troy Hills | 2006 |
| Avnet | business, public company | Phoenix | 1921 |
| Avon Products Inc. | multi-level marketing company, public company | New York City | 1886 |
| Awty International School | school, private school | — | 1956 |
| Axios | news website, business | Arlington County | 2017 |
| Babcock & Wilcox | business, enterprise, public company | Charlotte, United States, New York City | 1867 |
| Babson College | private not-for-profit educational institution | — | September 3, 1919 |
| Backbone Entertainment | video game developer | Emeryville | 2003 |
| Bad Boy Records | record label, music publisher, imprint, music organization | Washington, D.C. | 1993 |
| Bad Robot Productions | television production company, film production company | Santa Monica | 1998 |
| Baen Books | book publisher, publishing house | Wake Forest | 1983 |
| Bain & Company | management consulting company | Boston | 1973 |
| Baker Hughes | business, enterprise, public company | Houston | 1987 |
| Baker Motor Vehicle | business, automobile manufacturer | Cleveland | 1899 |
| Baldwin Piano Company | business | Trumann | 1862 |
| Ball Aerospace & Technologies | former entity, subsidiary company, aerospace manufacturer | Boulder | 1956 |
| Baltimore Museum of Art | nonprofit organization, art museum, publishing house, museum building | Baltimore | 1914 |
| Banana Republic | business, enterprise, clothing store chain | San Francisco | 1978 |
| Bandcamp | music streaming service, digital distribution platform, online music store | Oakland | 2007 |
| Bantam Books | publishing house, imprint | New York City | 1945 |
| Bard College | liberal arts college, private not-for-profit educational institution | — | 1860 |
| Barry University | private not-for-profit educational institution, university | — | 1940 |
| Basecamp | business, enterprise | Chicago | 2004 |
| Baskin-Robbins | food manufacturing, business, enterprise, ice cream parlor chain | Canton | 1945 |