| ASICS | multinational corporation, public company | Kobe | 1949 |
| ASM International | engineering society, publishing house, organization | ASM Headquarters and Geodesic Dome | 1913 |
| Aspen Music Festival and School | annual event, nonprofit organization, conservatory, music festival | — | 1949 |
| Aspyr | video game publisher, video game developer | Austin | 1996 |
| Association for Computational Linguistics | publishing house, open-access publisher, learned society | Stroudsburg | 1962 |
| Association for Computing Machinery | regulatory college, publishing house, organization, open-access publisher, scientific society, learned society | New York City | September 15, 1947 |
| AST Research | business | Irvine | 1980 |
| AT&T Corporation | concern, business, enterprise | Boston, Texas, 550 Madison Avenue, Dallas, United States, 195 Broadway, New York City, Bedminster | March 3, 1885 |
| AT&T Mobility | mobile network operator, telecommunications company | Atlanta | 2001 |
| ATA Airlines | airline | Indianapolis | 1973 |
| Atari Games | video game publisher, video game developer | Milpitas | July 1984 |
| Atari, Inc. | video game publisher, video game developer | New York City | February 1993 |
| Atari, Inc. | video game publisher | New York City | February 1993 |
| Atchison, Topeka and Santa Fe Railway | railway company | Chicago | 1895 |
| Atlantic Southeast Airlines | airline | Hartsfield–Jackson Atlanta International Airport | 1979 |
| Atlas Obscura | publishing house, brand, online encyclopedia, database | Greenpoint | 2009 |
| Au Bon Pain | business | Boston | 1978 |
| Audiomachine | musical group, enterprise | Los Angeles | August 20, 2005 |
| Augusta National Golf Club | golf course, golf club, business | — | 1930 |
| Aurora University | private not-for-profit educational institution, university | Aurora | 1893 |
| AutoZone | car parts shop chain, public company | Memphis | 1979 |
| Avatar Press | comics publishing company, book publisher, business, enterprise | Rantoul | 1996 |
| Avery Dennison | public company | Glendale | 1935 |
| Avid Audio | business, subsidiary company | Daly City | 1984 |
| Avis Budget Group | business, public company | Parsippany-Troy Hills | 2006 |
| Awty International School | school, private school | — | 1956 |
| Axios | news website, business | Arlington County | 2017 |
| Azusa Pacific University | church college, private not-for-profit educational institution, seminary, university | — | 1899 |
| Aéropostale | clothing store chain, public company | New York City | 1973 |
| Babcock & Wilcox | business, enterprise, public company | Charlotte, United States, New York City | 1867 |
| Babson College | private not-for-profit educational institution | — | September 3, 1919 |
| Baen Books | book publisher, publishing house | Wake Forest | 1983 |
| Bain & Company | management consulting company | Boston | 1973 |
| Baker Motor Vehicle | business, automobile manufacturer | Cleveland | 1899 |
| Baker University | private not-for-profit educational institution, private university | — | 1858 |
| Ball Corporation | business, enterprise, public company | Broomfield | 1880 |
| Banana Republic | business, enterprise, clothing store chain | San Francisco | 1978 |
| Bank of America Home Loans | business, credit institution | Charlotte | 2009 |
| Bank of America Merrill Lynch | business | Bank of America Tower | 2009 |
| Bantam Books | publishing house, imprint | New York City | 1945 |
| Bare Knuckle Fighting Championship | business | Philadelphia | 2018 |
| Barry University | private not-for-profit educational institution, university | — | 1940 |
| Baruch College | public educational institution of the United States, university | New York City | 1919 |
| Bates College | liberal arts college, private not-for-profit educational institution | — | 1855 |
| Bausch Health | pharmaceutical company, business, public company | Laval, Wilmington | 1960 |
| BBDO | advertising agency | New York City | 1891 |
| BEA Systems | business, public company | San Jose | 1995 |
| Beats Electronics | business, enterprise | Culver City | 2006 |