| Name | What | Region | Country | Lat | Long | Elev ft. | Pop est |
|---|---|---|---|---|---|---|---|
| Oak Acres | city | Delaware | United States | 38.49 | -75.11 | 19 | |
| Oak Drive | city | Delaware | United States | 38.59 | -75.31 | 22 | |
| Oak Forest Estates | city | Delaware | United States | 39.18 | -75.70 | 45 | |
| Oak Forest Mobile Home Park | city | Delaware | United States | 38.63 | -75.17 | 9 | |
| Oak Grove | city | Delaware | United States | 38.66 | -75.71 | 39 | |
| Oak Grove | city | Delaware | United States | 39.16 | -75.49 | 3 | |
| Oak Hollow | city | Delaware | United States | 39.66 | -75.64 | 49 | |
| Oak Lane Manor | city | Delaware | United States | 39.79 | -75.53 | 265 | |
| Oak Meadows Mobile Home Park | city | Delaware | United States | 38.61 | -75.20 | 6 | |
| Oak Orchard | city | Delaware | United States | 38.60 | -75.17 | 0 | |
| Oak Orchard West Mobile Home Park | city | Delaware | United States | 38.61 | -75.20 | 6 | |
| Oak Point Acres | city | Delaware | United States | 39.10 | -75.66 | 49 | |
| Oak Shadows | city | Delaware | United States | 39.18 | -75.49 | 3 | |
| Oakdale | city | Delaware | United States | 39.67 | -75.70 | 49 | |
| Oakland | city | Delaware | United States | 39.68 | -75.76 | 121 | |
| Oakley | city | Delaware | United States | 38.81 | -75.49 | 49 | |
| Oakmont | city | Delaware | United States | 39.71 | -75.55 | 32 | |
| Oaknoll | city | Delaware | United States | 39.03 | -75.56 | 49 | |
| Oaktree Apartments | city | Delaware | United States | 39.65 | -75.78 | 170 | |
| Oakwood Hills | city | Delaware | United States | 39.76 | -75.67 | 259 | |
| Ocean View | city | Delaware | United States | 38.55 | -75.09 | 13 | |
| Ocean Village | city | Delaware | United States | 38.56 | -75.06 | 3 | |
| Ocean Way Estates | city | Delaware | United States | 38.54 | -75.08 | 13 | |
| Odessa | city | Delaware | United States | 39.46 | -75.66 | 42 | |
| Odessa Heights | city | Delaware | United States | 39.45 | -75.66 | 42 | |
| Ogletown | city | Delaware | United States | 39.68 | -75.70 | 49 | |
| Old Furnace | city | Delaware | United States | 38.67 | -75.52 | 19 | |
| Old Landing | city | Delaware | United States | 38.69 | -75.13 | 0 | |
| Old Landing | city | Delaware | United States | 38.58 | -75.27 | 19 | |
| Old Landing Woods | city | Delaware | United States | 38.70 | -75.13 | 3 | |
| Old Mill Acres | city | Delaware | United States | 38.60 | -75.64 | 19 | |
| Old Mill Manor | city | Delaware | United States | 39.69 | -75.70 | 49 | |
| Omar | city | Delaware | United States | 38.53 | -75.20 | 19 | |
| Orchard Acres | city | Delaware | United States | 39.03 | -75.54 | 39 | |
| Orchard Manor | city | Delaware | United States | 38.60 | -75.18 | 3 | |
| Otters Run | city | Delaware | United States | 39.03 | -75.50 | 3 | |
| Overbrook | city | Delaware | United States | 38.77 | -75.21 | 19 | |
| Overbrook Shores | city | Delaware | United States | 38.76 | -75.23 | 19 | |
| Overlook Colony | city | Delaware | United States | 39.80 | -75.47 | 91 | |
| Overview Gardens | city | Delaware | United States | 39.71 | -75.57 | 45 | |
| Owens | city | Delaware | United States | 38.81 | -75.53 | 49 | |
| Owls Nest | city | Delaware | United States | 39.81 | -75.63 | 298 | |
| Oxyoke Mobile Home Park | city | Delaware | United States | 39.08 | -75.57 | 49 | |
| Oyster Rocks | city | Delaware | United States | 38.80 | -75.20 | 3 |