| 100th Training Division (Leader Development) | airborne infantry division, United States Army infantry division, training division | Fort Knox | 1918 |
| 20th Century Animation | television production company, animation studio, film production company | Century City | February 1994 |
| 20th Century Fox Television | television production company | Los Angeles | 1949 |
| 20th Century Studios | television production company, production company, film production company, film studio | Fox Plaza, Walt Disney Studios | 1985 |
| 21 Club | restaurant | — | 1922 |
| 2K | video game publisher, video game developer | Novato | 2005 |
| 3D Systems | business, public company | Rock Hill | 1986 |
| 3M | business, conglomerate, public company | Maplewood | 1902 |
| 4Kids TV | television production company, television channel | — | September 14, 2002 |
| 88rising | media company, record label | New York City | July 30, 2015 |