| 1301 | OHCR | The Columbus & Ohio River R.R. Co. | added 10/92 | | NRHS |
| 1302 | OHCR | Ohio Central R.R. Inc. | 1/94-7/2000 | | NRHS |
| 1303 | OHCR | OHIO CENTRAL RAILROAD, INC. [COLUMBUS & OHIO RIVER RAILROAD CO.] | | | PWRC |
| 1304 | OHCR | Ohio Central Railroad | | | RSRV |
| 1305 | OHCR | OHIO CENTRAL RAILROAD CO | | | SCAC3 |
| 1306 | OHCR | OHIO CENTRAL RAILROAD CO | | | SCAC4 |
| 1307 | OHCR | Ohio Central Railroad Inc | | USA | TRAFFIC |
| 1308 | OHCX | Stauffer Chemical Co. — Eastern Branch | added 4/1965; 7/1965 (not listed) | | NAKINA |
| 1309 | OHCX | Old Hickory Chemical Co. | 7/1932-4/1961; eliminated 1/1965 | | NAKINA |
| 1310 | OHCX | Old Hickory Chemical Co. | 4/38-4/61; eliminated 1/65 | | NRHS |
| 1311 | OHCX | Stauffer Chemical Co. -- Eastern Branch | added 4/65; 7/65 | | NRHS |
| 1312 | OHCX | STAUFFER CHEMICAL CO. - EASTERN BRANCH [OLD HICKORY CHEMICAL CO.] | | | PWRC |
| 1313 | OHDI | OHIO DISPATCH INC | | | SCAC3 |
| 1314 | OHDL | OMAHA DIRECT LLC | | | SCAC4 |
| 1315 | OHE | Osthavelländische Eisenbahn Berlin-Spandau AG | Berlin | D | privat-bahn.de |
| 1316 | OHE | Osthannoversche Eisenbahn AG | Celle | D | privat-bahn.de |
| 1317 | OHE | Osthannoversche Eisenbahnen | | D | TRAFFIC |
| 1318 | OHE | Osthannoversche Eisenbahnen | | DE | VKM |
| 1319 | OHEE | OHIO EASTERN EXPRESS INC | | | SCAC3 |
| 1320 | OHEE | OHIO EASTERN EXPRESS INC | | | SCAC4 |
| 1321 | OHEGO | OHE Cargo GmbH | | DE | VKM |
| 1322 | OHER | OTTERHOLE MANAGEMENT LLC | | | SCAC4 |
| 1323 | OHESP | Osthavelländische Eisenbahnen Berlin-Spandau AG | Real: OHE-SP | D | TRAFFIC |
| 1324 | OHFX | Fluor Daniel Fernald | 7/2000-7/2005 (not listed) | | NAKINA |
| 1325 | OHFX | Fluor Daniel Fernald | Jul-00 | | NRHS |
| 1326 | OHFX | FLUOR DANIEL FERNALD | | | PWRC |
| 1327 | OHFX | Fluor Daniel Fernald | | | RSRV |
| 1328 | OHFX | US DEPARTMENT OF ENERGY EM CONSOLID | | | SCAC4 |
| 1329 | OHGI | OLLENDORFF, H G INC | | | SCAC3 |
| 1330 | OHGI | OCHOA GONZALEZ, RODRIGO | | | SCAC4 |
| 1331 | OHGR | OLIVARES HERNANDEZ GONZALO, RAUL | | | SCAC4 |
| 1332 | OHGX | Otha H. Grimes (Grimes Gasoline Co.) | 7/1937-4/1938; 1/1943-7/1954 | | NAKINA |
| 1333 | OHGX | Otha H. Grimes | 7/1930-7/1935 | | NAKINA |
| 1334 | OHGX | Otha H. Grimes | Apr-38 | | NRHS |
| 1335 | OHGX | Otha H. Grimes (Grimes Gasoline Co.) | Jan-52 | | NRHS |
| 1336 | OHGX | GRIMES GASOLINE CO. [OTHA H. GRIMES] | | | PWRC |
| 1337 | OHHG | OLINGER HEAVY HAULING | | | SCAC4 |
| 1338 | OHHL | O H HUNT LINE INC | | | SCAC3 |
| 1339 | OHIC | Ohi-Rail Corp. | added 10/1982; eliminated 10/1987; eliminated 1/1991; 1/1994-7/2005 | | NAKINA |
| 1340 | OHIC | Ohi-Rail Corp. | added 10/82; eliminated 10/87; eliminated 1/91; 1/94-7/2000 | | NRHS |
| 1341 | OHIC | OHI-RAIL CORPORATION | | | PWRC |
| 1342 | OHIC | Ohi-Rail Corporation | | | RSRV |
| 1343 | OHIC | OHI-RAIL CORPORATION | | | SCAC3 |
| 1344 | OHIE | OHIO INTRA EXPRESS INC | | | SCAC3 |
| 1345 | OHIE | OHIO INTRA EXPRESS INC | | | SCAC4 |
| 1346 | OHIQ | OHIO TRANSFER INC | | | SCAC3 |
| 1347 | OHJ | Odsherred Jernbane (Odsherredsbanen) | 1899 - 2003 | DK | jernbanen.dk |
| 1348 | OHJ | Orsa - Härjedalen Järnväg | 1908 - 1919 | S | svenska-lok.se |
| 1349 | OHJ | Odsherred Jernbane (Odsherredsbanen) | 1899 - 2003 | DK | TRAFFIC |
| 1350 | OHK | Oasis Hong Kong Airlines Limited | IATA: O8, Callsign: Oasis, IATA Prefix: 558, Ceased Operations | HK | AVCODES |
| 1351 | OHK | Oasis Hong Kong Airlines | IATA: O8 | | ICAO1 |
| 1352 | OHK | Oasis Hong Kong Airlines | | HK | TRAFFIC |
| 1353 | OHKU | TOK AMERICA | | USA | BIC |
| 1354 | OHKU | OHKA AMERICAN INCORPORATED USA | | | PWRC |
| 1355 | OHKU | Ohka American | | | RSRV |
| 1356 | OHKY | OHIO-KENTUCKY STEEL CORP | | | SCAC3 |
| 1357 | OHLB | OHL BROTHERS FARMS | | | SCAC3 |
| 1358 | OHLC | OHLCO INC | | | SCAC4 |
| 1359 | OHLD | OHL DISTRIBUTING | | | SCAC4 |
| 1360 | OHLO | OHIO LOGISTICS | | | SCAC4 |
| 1361 | OHLR | OHLERS TOWING SERVICE | | | SCAC3 |
| 1362 | OHLR | O'HALLORAN, P E INC | | | SCAC4 |
| 1363 | OHLT | OHL DISTRIBUTING (REFRIGERATED) | | | SCAC4 |
| 1364 | OHLY | OHLEY TRANSFER COMPANY | | | SCAC3 |
| 1365 | OHMC | OHM CYCLES LTD | | | SCAC4 |
| 1366 | OHMI | ONE HOUR MESSENGER INC | | | SCAC4 |
| 1367 | OHMK | O H MELING TANKERS KS | | | SCAC4 |
| 1368 | OHMS | OLIVE HILL MOTOR SALES INC | | | SCAC3 |
| 1369 | OHMT | OHIO MOBILE TRANSPORT | | | SCAC3 |
| 1370 | OHMV | OLD HARBOR MOVING & STORAGE INC | | | SCAC3 |
| 1371 | OHNT | OHIO NORTHERN TRANSIT CO | | | SCAC3 |
| 1372 | OHNT | OHIO NORTHERN TRANSIT CO | | | SCAC4 |
| 1373 | OHOX | U.S. Dept. of Energy Ohio Field | 7/2000-7/2005 (not listed) | | NAKINA |
| 1374 | OHOX | U.S. Dept. of Energy Ohio Field | Jul-00 | | NRHS |
| 1375 | OHOX | U.S. DEPARTMENT OF ENERGY OHIO FIELD | | | PWRC |
| 1376 | OHOX | United States Department of Energy Ohio Field | | | RSRV |
| 1377 | OHPA | Ohio & Pennsylvania R.R. Co. | added 10/1995; 7/2000-7/2005 | | NAKINA |
| 1378 | OHPA | Ohio & Pennsylvania R.R. Co. | added 10/95; 7/2000 | | NRHS |
| 1379 | OHPA | OHIO & PENNSYLVANIA RAILROAD | | | PWRC |
| 1380 | OHPA | Ohio and Pennsylvania Railroad | | | RSRV |
| 1381 | OHPA | OHIO & PENNSYLVANIA RAILROAD COMPAN | | | SCAC4 |
| 1382 | OHPE | OHIO PACIFIC EXPRESS INC | | | SCAC3 |
| 1383 | OHPE | OHIO PACIFIC EXPRESS INC | | | SCAC4 |
| 1384 | OHPT | OHIO PIGGYBACK TRANSPORTATION INC | | | SCAC3 |
| 1385 | OHPX | Merchants Despatch Transportation Corp. | added 1/1955; 10/1957-4/1961; eliminated 1/1964 | | NAKINA |
| 1386 | OHPX | Merchants Despatch Transportation Corp. | 10/57-4/61 | | NRHS |
| 1387 | OHPX | MERCHANTS DESPATCH TRANSPORTATION CORP. | | | PWRC |
| 1388 | OHRA | OHARA TRUCKING CO, INC | | | SCAC3 |
| 1389 | OHRC | OHIO RUBBER CO | | | SCAC3 |
| 1390 | OHRE | OHARE FREIGHT FORWARDERS INC | | | SCAC3 |
| 1391 | OHRM | OHRMAN, LEE TRUCKING | | | SCAC3 |
| 1392 | OHRP | OHIO RIVER PIPE LINE COMPANY | | | SCAC3 |
| 1393 | OHRY | Owego and Harford Ry., Inc. | added 7/1992; 1/1994-7/2005; eliminated 10/2009 | | NAKINA |
| 1394 | OHRY | Owego and Harford Ry., Inc. | added 7/92; 1/94-7/2000 | | NRHS |
| 1395 | OHRY | OWEGO & HARTFORD RAILWAY, INC | | | PWRC |
| 1396 | OHRY | Owego and Harford Railway | | | RSRV |
| 1397 | OHRY | OWEGO & HARFORD RAILWAY INC | | | SCAC4 |
| 1398 | OHS | Odengene Air Shuttle Services Limited | Callsign: Odengene, | WAN | AVCODES |
| 1399 | OHSB | OHIO-SEABOARD TRANSIT INC | | | SCAC3 |
| 1400 | OHSC | OHIO STAVE COMPANY | | | SCAC3 |
