| SideBench | California |
| Sidebum Studios | California |
| SideChannel | Massachusetts |
| SideKick | Texas |
| Sidekick Bio, Inc. | |
| Sidekick Browser | |
| Sidekick Creative Agency | |
| SideKick, Inc. | Minnesota |
| Sideqik | Georgia |
| Sidereal Therapeutics | |
| Sidero Labs | |
| SideSmile, Inc. | New Jersey |
| Sidestep Technologies, Inc. | |
| Sidetrips, Inc. | Tennessee |
| Sideways Designs | |
| Sidewinder Therapeutics, Inc. | |
| Sidework | |
| Sidus Space | |
| Siege Media | |
| Siemba, Inc. | Georgia |
| Siemplify | New York |
| Siena College Computer Science | New York |
| Siena College Mathematics | New York |
| Siena Heights University | Michigan |
| Siena Labs, Inc. | |
| Sienna Corporation | Georgia |
| Siepe, LLC | Texas |
| Sierra Analytics, Inc. | California |
| Sierra Circuits, Inc. | California |
| Sierra College | California |
| Sierra Communications, Inc. | Maine |
| Sierra Components, Inc. | Nevada |
| Sierra Computer Group | Nevada |
| Sierra Consulting | |
| Sierra Data Centers | Pennsylvania |
| Sierra Electronics | Nevada |
| Sierra Experts | Pennsylvania |
| Sierra IC, Inc. | North Carolina |
| Sierra Information Systems, Inc. | Georgia |
| Sierra Integrated Systems | Nevada |
| Sierra Interactive | Kentucky |
| Sierra Internet Services | Nevada |
| Sierra Microproducts, Inc. | Washington |
| Sierra National Corporation | California |
| Sierra Nevada Corporation | Nevada |
| Sierra Remote Observatories | |
| Sierra Sciences | |
| Sierra Space | |
| Sierra Space Corporation | Colorado |
| Sierra Space Ventures | |