| Abbreviation | Definition |
|---|---|
| IORY | Indiana and Ohio Railway |
| IORY | Indiana and Ohio Railway Company |
| IOSX | Indiana & Ohio Scenic Rail Corporation |
| IOWZ | Iowa Ethanol |
| IPAZ | Illinois International Port Authority |
| IPBX | INNOPHOS Inc. |
| IPC | International Paper Company |
| IPCJ | Indiana Port Commission |
| IPCU | Independent Container Line |
| IPCX | International Paper |
| IPCX | International Paper Company |
| IPCZ | International Paper Company |
| IPEX | Indeck Power Equipment |
| IPEX | Indeck Power Equipment Company |
| IPLX | Illinois Power |
| IPLX | Illinois Power Company |
| IPOX | A and R Leasing |
| IPOX | A and R Leasing, Limited Liability Corporation |
| IPPX | Intermountain Power Agency |
| IPSX | MidAmerican Energy Company |