| Odyssey Marine Exploration | Tampa | 1994 |
| OfficeMax | — | 1988 |
| Ohio Valley Wrestling | Louisville | 1997 |
| Old Navy | São Francisco | 1994 |
| Olin Corporation | Clayton | 1892 |
| On2 Technologies | Nova Iorque | 1999 |
| ONErpm | Brooklyn | 2010 |
| Oneworld | Fort Worth | 1999 |
| Onsemi | Scottsdale | 18 de junho de 1992 |
| OpenDNS | São Francisco | julho 2006 |
| OQO | São Francisco | 2000 |
| Oracle Corporation | Austin | 16 de junho de 1977 |
| Orbcomm | Fort Lee | 1993 |
| Organon & Co. | Oss | 1923 |
| Orion Pictures | Los Angeles | janeiro 1978 |
| Osborne Computer Corporation | Hayward | 27 de setembro de 1979 |
| Otis Elevator Company | Farmington | 1853 |
| Overbrook Entertainment | Beverly Hills, Los Angeles | 1998 |
| Packard Bell | Chatsworth | 1926 |
| Padlet | São Francisco | 1 de dezembro de 2012 |
| Palantir Technologies | Miami | 2003 |
| Panic Inc. | Portland, Oregon | — |
| Pantone | Carlstadt | 1962 |
| Paper Mate | Oak Brook | 1940 |
| Parallels | Renton | 1999 |
| Parametric Technology Corporation | Boston | maio 1985 |
| Paramount Animation | Los Angeles | 2011 |
| Parker Brothers | Beverly, Salém | 1883 |
| Parker Guitars | Buffalo Grove | 1993 |
| Participant | Los Angeles | janeiro 2004 |
| Payoneer | Nova Iorque | 2005 |
| Peerless | Cleveland | 1900 |
| Peet's Coffee | Emeryville | 1966 |
| Pennzoil | Houston | 1963 |
| Pentaho | Orlando | 2004 |
| Perplexity.ai | São Francisco | 7 de dezembro de 2022 |
| Petco | San Diego | 1965 |
| PetSmart | Phoenix | 1986 |
| Philip Morris International | Stamford, Lausana | 1987 |
| Phillips 66 | Westchase | 1 de maio de 2012 |
| Pierce-Arrow | Buffalo | 1870 |
| Pilgrim's Pride | Greeley | 1946 |
| Pitney Bowes | Stamford | 1920 |
| Planet Labs | São Francisco | 28 de dezembro de 2010 |
| Plantronics | Santa Cruz | 1961 |
| PlayStation Now | Aliso Viejo | novembro 2008 |
| Plug Power | Latham, Slingerlands | 1997 |
| Polycom | São José | 1990 |