| Name | What | Region | Country | Lat | Long | Elev ft. | Pop est |
|---|---|---|---|---|---|---|---|
| O'Brien | city | Provincia de Buenos Aires | Argentina | -34.90 | -60.75 | 180 | 1774 |
| O'Higgins | city | Provincia de Buenos Aires | Argentina | -34.58 | -60.70 | 209 | 5981 |
| O. Aballe | city | Provincia de Buenos Aires | Argentina | -39.13 | -62.60 | 29 | 0 |
| O. Basualdo | city | Provincia de Buenos Aires | Argentina | -34.03 | -60.67 | 213 | 322 |
| Obligado | city | Provincia de Buenos Aires | Argentina | -33.58 | -59.82 | 9 | 639 |
| Ochandio | city | Provincia de Buenos Aires | Argentina | -38.35 | -59.78 | 318 | 0 |
| Olascoaga | city | Provincia de Buenos Aires | Argentina | -35.20 | -60.60 | 177 | 447 |
| Olavarría | city | Provincia de Buenos Aires | Argentina | -36.90 | -60.28 | 534 | 19817 |
| Olavarría | city | Provincia de Buenos Aires | Argentina | -35.70 | -63.00 | 321 | 749 |
| Oliden | city | Provincia de Buenos Aires | Argentina | -35.18 | -57.95 | 65 | 564 |
| Olivera | city | Provincia de Buenos Aires | Argentina | -34.63 | -59.25 | 98 | 2974 |
| Olivos | city | Provincia de Buenos Aires | Argentina | -34.51 | -58.50 | 62 | 602683 |
| Ombucta | city | Provincia de Buenos Aires | Argentina | -38.90 | -62.53 | 68 | 0 |
| Ombucto | city | Provincia de Buenos Aires | Argentina | -38.90 | -62.53 | 68 | 0 |
| Ombú | city | Provincia de Buenos Aires | Argentina | -37.13 | -62.03 | 554 | 149 |
| Open Door | city | Provincia de Buenos Aires | Argentina | -34.50 | -59.08 | 91 | 23234 |
| Ordoqui | city | Provincia de Buenos Aires | Argentina | -35.90 | -61.17 | 275 | 298 |
| Orense | city | Provincia de Buenos Aires | Argentina | -38.67 | -59.78 | 104 | 2290 |
| Oriente | city | Provincia de Buenos Aires | Argentina | -38.73 | -60.62 | 137 | 1438 |
| Ortiz Basualdo | city | Provincia de Buenos Aires | Argentina | -34.03 | -60.67 | 213 | 322 |
| Ortiz de Rosas | city | Provincia de Buenos Aires | Argentina | -35.40 | -60.38 | 193 | 298 |
| Ortiz de Rozas | city | Provincia de Buenos Aires | Argentina | -35.40 | -60.38 | 193 | 298 |
| Ostende | city | Provincia de Buenos Aires | Argentina | -37.15 | -56.88 | 3 | 13671 |
| Ostendi | city | Provincia de Buenos Aires | Argentina | -37.15 | -56.88 | 3 | 13671 |
| Otamendi | city | Provincia de Buenos Aires | Argentina | -34.23 | -58.86 | 13 | 8901 |
| O’Brien | city | Provincia de Buenos Aires | Argentina | -34.90 | -60.75 | 180 | 1774 |
| O’Higgins | city | Provincia de Buenos Aires | Argentina | -34.58 | -60.70 | 209 | 5981 |