| Marcel Digital | |
| MarcelHeap | |
| MarcelTech | Delaware |
| March Biosciences | |
| March Capital Venture Management Services, LLC | California |
| Marchand Electronics, Inc. | New York |
| Marchese Computer Products, Inc. | New York |
| Marchex, Inc. | Washington |
| Marci, Inc. | Minnesota |
| Marcinetworkhardware | Texas |
| MarCom new Media | California |
| MarcomCentral | California |
| Marconi Pacific, LLC | Maryland |
| Marcopolis, LLC | |
| MarcoPolo Learning, Inc. | |
| Marcum Creative, LLC | Oklahoma |
| Marcus Thomas, LLC | |
| Marcy Design Group, Inc. | |
| Marea Therapeutics, Inc. | |
| Marecomms, Inc. | |
| Marengo Therapeutics, Inc. | |
| Margasoft Corporation | |
| MarginEdge | Virginia |
| MarginMAX | Louisiana |
| Margret\A Consulting, LLC | Illinois |
| Maria College | New York |
| MariaDB | California |
| Marian University Department of Mathematical and Computational Science | Indiana |
| Marian University Indianapolis | Indiana |
| Marian University Wisconsin | Wisconsin |
| Mariana Oncology | Massachusetts |
| Mariana Trench | |
| Maricopa Controls, Inc. | Arizona |
| Marietta College | Ohio |
| Marigold | Tennessee |
| Marigold Direct | Washington |
| Marin Biologic Laboratories, Inc. | California |
| Marin Consulting, Inc. | California |
| Marin Software | California |
| Marina Pointe Tech Support | California |
| MarinaWare | Washington |
| Mariner Software | Minnesota |
| Marinus Analytics | Pennsylvania |
| Mario Hernandez | California |
| Marion Integrated Marketing | Texas |
| Marion Street Capital | Pennsylvania |
| Marion Technical College | Ohio |
| Maris Consulting Group | |
| Marisa Gonzales Studios, LLC | |
| Marist College | New York |