| Abbreviation | Definition |
|---|---|
| MSWJ | Midland and South Western Junction Railway |
| MSWY | Minnesota Southern Railway |
| MT | Micro-Trains |
| MT | Mississippi and Tennessee RailNet |
| MT | Mississippi and Tennessee RailNet Incorporated |
| MTAX | MTAX Corporation |
| MTC | Mystic Terminal |
| MTCO | Macon Terminal |
| MTCO | Macon Terminal Company |
| MTCX | Mallard Transportation |
| MTCX | Mallard Transportation Company |
| MTCZ | Mayflower Transit and Storage |
| MTDX | Midwest Transportation and Development |
| MTFR | Minnesota Transfer Railway |
| MTGU | Matheson Tri-Gas |
| MTIU | Miller Intermodal Logistics Services |
| MTIU | Welfit Oddy (PTY) Limited |
| MTIZ | American Marine Industries |
| MTIZ | Mississippi Transportation Inc. (American Marine Industries) |
| MTLU | Montgomery Tank Lines |