| STATION | CODE | STATION | CODE | STATION | CODE |
| O D E | 2692 | Olagadam Nallroad | 4256 | Orathy | 4115 |
| O K Mittur | 8159 | Olakkur | 4147 | Ordinance factory | 7572 |
| O.D.Cheruvu | 8494 | Olapalayam | 4257 | Orgram | 3452 |
| Oachira | 476 | Olatpur | 6724 | Ormanjhi | 651 |
| Obedullaganj | 7480 | Old Thiruverumbur | 431 | Oruvandhurpudur | 4286 |
| Oblapura | 8190 | Ollur | 487 | Orvakallu | 8518 |
| Obra | 54466 | Olpad | 26212 | Osian | 2922 |
| Obulavaripalli | 8566 | Omalur | 4290 | Osmanabad | 2472 |
| Ochhan | 2641 | Omassery | 495 | Osur | 4183 |
| Odagaon | 675383 | Omerga | 2475 | Otha | 2844 |
| Odaipatti | 4553 | OMPI | 3825 | Othakadai | 452 |
| Odakali | 484 | Ongallur | 4926 | Othera | 469 |
| Oddanchatram | 4553 | Ongole | 8592 | Othian | 1858 |
| Odeyarapalya | 8225 | Oni | 2353 | Othihal | 8424 |
| Odlabari | 3562 | Onipeta | 8564 | Ottangadu | 4373 |
| Odugathur | 4171 | Onjal | 2637 | Ottapalam | 4926 |
| Oel | 5872 | Onnupuram | 4173 | Ottapidaram | 461 |
| Oft-Trichy | 431 | Oonnukal | 485 | Ottasekaramangalam | 471 |
| Ognaj | 2717 | Ooty | 423 | Otur | 2132 |
| Oinam | 3879 | Oppilan | 4576 | Oupada | 6782 |
| Okha | 2892 | Orai | 5162 | Outsurangaplalle | 8753 |
| Okkanadukeelaiyur | 4372 | Orai | 5162 | Owk | 8515 |
| Okkur | 4575 | Oran | 2770 | Ozar | 2132 |
| Olagadam | 4256 | Orathanadu | 4372 | Ozar | 2550 |
| Ozarde | 2167 | | | | |
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