List of std code of areas name start with letter O
| Place | STD CODE | |
| Outsarangapalle (Andhra Pradesh) | : | 8753 |
| Ongole (Andhra Pradesh) | : | 8592 |
| Odgi (Chhattisgarh) | : | 7773 |
| Okha (Gujarat) | : | 2892 |
| Omerga (Maharashtra) | : | 2475 |
| Osmanabad (Maharashtra) | : | 2472 |
| Osian(e) (Rajasthan) | : | 2927 |
| Osian(n) (Rajasthan) | : | 2922 |
| Osian(s) (Rajasthan) | : | 2926 |
| Oddanchatram (Tamil Nadu) | : | 4553 |
| Ootacamund (Tamil Nadu) | : | 423 |
| Omalpur (Tamil Nadu) | : | 4290 |
| Orathanad (Tamil Nadu) | : | 4372 |
| Orai (Uttar Pradesh) | : | 5162 |