| L3Harris Technologies | business, public company | Melbourne | June 29, 2019 |
| La Salle University | private not-for-profit educational institution, Catholic university | — | 1863 |
| La Senza | business, clothing store chain | Montreal | 1990 |
| La-Z-Boy | business, public company | Monroe | 1927 |
| Lafayette College | liberal arts college, private not-for-profit educational institution | Easton | 1826 |
| Lake Torpedo Boat Company | shipbuilding company | Bridgeport | 1901 |
| Lakeside School | school, private school | — | 1919 |
| Landmark Worldwide | business, enterprise | San Francisco | 1991 |
| Langston University | historically black college or university, public educational institution of the United States, school, land-grant university, public university | — | 1897 |
| Language Creation Society | business | Garden Grove | 2007 |
| Lanteris Space Systems | privately held company, subsidiary company | Palo Alto | 1957 |
| Las Vegas Sands | business, enterprise, public company | Las Vegas, Paradise | 1937 |
| LaSalle | automobile manufacturer | Detroit | 1927 |
| 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 |
| Lazard | business, credit institution, public company | New York City | July 12, 1848 |
| LeCroy Corporation | business, enterprise | Chestnut Ridge | 1964 |
| Legendary Pictures | film production company | Burbank | 2000 |
| Lehigh University | private not-for-profit educational institution, university, academic publisher | Bethlehem | 1865 |
| Lehman Brothers | investment bank, business, public company | New York City | 1850 |
| Lemonade | insurance company, public company | New York City | 2015 |
| LenovoEMC | business, enterprise | San Diego | 1980 |
| Level 3 Communications | business, enterprise, public company | Frankfurt | 1985 |
| Levi Strauss & Co. | business, retail chain, enterprise, brick and mortar, public company | San Francisco, Levi's Plaza | 1853 |
| Lexicon | business | Woodbury | 1971 |
| Lexmark | business, enterprise | Lexington | March 27, 1991 |
| Liberty University | church college, private not-for-profit educational institution, university, Christian organization | — | 1971 |
| Library of America | nonprofit organization, publishing house, book series | New York City | 1979 |
| Lightstorm Entertainment | film production company | Santa Monica | 1990 |
| Lime | startup company, dockless bicycle sharing system, business, e-scooter-sharing system | San Mateo | January 2017 |
| 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 |
| Lionbridge | business, enterprise, public company | Waltham | 1996 |
| Little Caesars | fast food restaurant chain, pizzeria chain | Detroit | May 8, 1959 |
| Little, Brown and Company | book publisher, publishing house | New York City | 1837 |
| Litton Industries | business, enterprise | Milwaukee | 1953 |
| Live Nation Entertainment | record label, entertainment company, public company | Beverly Hills | 2005 |
| Local Motors | automobile manufacturer | Phoenix | 2007 |
| 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 |
| Loma Linda University | church college, private not-for-profit educational institution, private university | Loma Linda | 1905 |
| Looking Glass Studios | video game developer | Cambridge | 1990 |
| Los Angeles Unified School District | school district in the United States | Los Angeles | 1961 |
| Lotus Software | business | Cambridge | 1982 |
| Lowe's | hardware store chain, public company | Mooresville | March 25, 1921 |
| 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 |
| Lucasfilm Games | video game publisher, video game developer | San Francisco, Letterman Digital Arts Center | May 1982 |
| Lunar and Planetary Laboratory | graduate school, research institute | — | 1960 |
| Luxor Resort & Casino | skyscraper, hotel | — | October 13, 1993 |
| Lycoming | business | Williamsport | 1845 |