| Kohlberg Kravis Roberts | investment company, financial services company, asset management company, business, private equity firm | New York City | 1976 |
| Kohn Pedersen Fox | architectural firm | Salmon Tower Building | 1976 |
| Kongregate | video game publisher, website | San Francisco | 2006 |
| Kraft Heinz | organization, business, enterprise, public company | Pittsburgh | 2015 |
| Kumon | supplementary educational institution for children, business, enterprise | Osaka | 1958 |
| La MaMa Experimental Theatre Club | theatre company | — | 1961 |
| La Salle University | private not-for-profit educational institution, Catholic university | — | 1863 |
| Lafayette College | liberal arts college, private not-for-profit educational institution | Easton | 1826 |
| Language Creation Society | business | Garden Grove | 2007 |
| Lantern Entertainment | film studio | Dallas | July 16, 2018 |
| Las Vegas Sands | business, enterprise, public company | Las Vegas, Paradise | 1937 |
| Laureate Education | international university, open-access publisher, education company, public company | Baltimore, Miami | 1998 |
| Lawrence University | liberal arts college, conservatory, Colleges That Change Lives, private not-for-profit educational institution, university | — | 1847 |
| Lay’s | business | — | 1934 |
| Lazard | business, credit institution, public company | New York City | July 12, 1848 |
| LCG Entertainment, Inc. | video game publisher, video game developer | Malibu | December 27, 2018 |
| Lear Corporation | business, public company | Southfield | 1917 |
| Leatherman | brand, business | Portland | 1983 |
| Legoland Florida | amusement park | — | October 15, 2011 |
| Lehman Brothers | investment bank, business, public company | New York City | 1850 |
| Lemonade | insurance company, public company | New York City | 2015 |
| Levi Strauss & Co. | business, retail chain, enterprise, brick and mortar, public company | San Francisco, Levi's Plaza | 1853 |
| Lexar | business | Milpitas | 1996 |
| Liberty Media | business, public company | Douglas County, Colorado | 1991 |
| Liberty Mutual Insurance | business, enterprise | Boston | 1912 |
| Lime | startup company, dockless bicycle sharing system, business, e-scooter-sharing system | San Mateo | January 2017 |
| Lincoln Motor Company | car brand, automobile manufacturer, public company | Dearborn | 1917 |
| Lincoln University | historically black college or university, public educational institution of the United States, public university | — | 1854 |
| Line 6 | business | Calabasas | 1996 |
| Ling-Temco-Vought | conglomerate | Cleveland | 1969 |
| Linotype | type foundry, private press | Brooklyn, Bad Homburg vor der Höhe | 1895 |
| Lionel Corporation | business, enterprise | New York City | 1900 |
| Little, Brown and Company | book publisher, publishing house | New York City | 1837 |
| Local Motors | automobile manufacturer | Phoenix | 2007 |
| Lockheed Martin | defense contractor, public company | Bethesda | 1995 |
| Loews Corporation | business, public company | New York City | 1946 |
| Logitech | software company, technology company, brand, business, public company | Lausanne, Newark | October 2, 1981 |
| Loki Entertainment | video game developer | Tustin | November 9, 1998 |
| Lollapalooza | business, music festival | — | 1991 |
| Lonely Planet | travel website, book publisher, business | Melbourne | 1972 |
| Long Island University | university | — | 1926 |
| Los Angeles Opera | nonprofit organization, opera company | Los Angeles | 1986 |
| Loyola Marymount University | Jesuit university, private not-for-profit educational institution, open-access publisher, private university | Los Angeles | 1865 |
| Loyola University New Orleans | private not-for-profit educational institution, university | — | 1904 |
| LSU New Orleans | public educational institution of the United States, university | — | 1958 |
| Lubin Manufacturing Company | film production company | Philadelphia | 1902 |
| Lucas Entertainment | pornographic film distributor, pornography website, pornographic film studio | New York City | 1998 |
| Lucasfilm | television production company, film production company, subsidiary company | San Francisco, Letterman Digital Arts Center, California | 1971 |