| Abbreviation | Definition |
|---|---|
| OKKT | Union Pacific Railroad Company |
| OLAU | Occidental Chemical Corporation |
| OLB | Omaha Lincoln and Beatrice Railway Company |
| OLB | Omaha, Lincoln and Beatrice Railway |
| OLDX | Old Line Holding |
| OLDX | Old Line Holdings Company Incorporated |
| OLEV | Operation Lifesaver Educational Vehicle (rail safety; Canada) |
| OLLU | Ocean Leasing |
| OLLU | Ocean Leasing Limited |
| OLNX | Olin Corporation |
| OLO | Ontario L'Orignal Railway |
| OLO | Ontario L'Orignal Railway Incorporated |
| OLYR | Olympic Railroad |
| OLYR | Olympic Railroad Company |
| OLYU | Olympic Container Corporation |
| OLYX | Olympia Petroleum |
| OLYZ | Showa Line |
| OLYZ | Showa Line Limited |
| OMAX | Omaha Public Power District |
| OMBU | Omnibox Container Management Services |