Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Our Saviour Evangelical Lutheran Church | Church | 134 | Baltimore (city) | 39 20 27 N | 076 41 02 W |
| Our Shepherd Lutheran Church | Church | 19 | Anne Arundel | 39 04 43 N | 076 34 13 W |
| Out Back | Locale | 0 | Dorchester | 38 28 42 N | 076 12 55 W |
| Out Point | Cape | 0 | Worcester | 38 13 26 N | 075 14 23 W |
| Outward Tump | Island | 0 | Worcester | 38 10 38 N | 075 11 53 W |
| Overbrook | Populated Place | 155 | Frederick | 39 26 05 N | 077 28 08 W |
| Overbrook (subdivision) | Populated Place | 33 | Prince George's | 38 59 44 N | 076 44 04 W |
| Overbrook Manor | Populated Place | 9 | Wicomico | 38 23 33 N | 075 35 60 W |
| Overlea | Populated Place | 69 | Baltimore | 39 21 48 N | 076 31 14 W |
| Overlea Baptist Church | Church | 76 | Baltimore (city) | 39 21 28 N | 076 31 51 W |
| Overlea High School | School | 41 | Baltimore | 39 20 57 N | 076 31 40 W |
| Overlea Middle School | School | 35 | Baltimore | 39 20 47 N | 076 30 57 W |
| Overlea United Methodist Church | Church | 81 | Baltimore (city) | 39 21 29 N | 076 31 57 W |
| Overlook | Populated Place | 149 | Baltimore | 39 28 43 N | 076 35 59 W |
| Overlook | Populated Place | 20 | Queen Anne's | 38 56 36 N | 076 07 49 W |
| Overlook (subdivision) | Populated Place | 128 | Frederick | 39 24 27 N | 077 26 30 W |
| Overlook Elementary School | School | 54 | Anne Arundel | 39 12 47 N | 076 39 06 W |
| Overlook Elementary School | School | 88 | Prince George's | 38 50 53 N | 076 57 03 W |
| Overlook Park | Park | 39 | Anne Arundel | 39 12 57 N | 076 39 14 W |
| Overshot Branch | Stream | | Harford | 39 30 22 N | 076 25 41 W |
| Overshot Run | Stream | | Baltimore | 39 29 21 N | 076 34 53 W |
| Overton | Populated Place | 3 | Kent | 39 01 58 N | 076 12 36 W |
| Overview Manor | Populated Place | 57 | Harford | 39 29 15 N | 076 18 01 W |
| Ovid Hazen Wells Recreational Park | Park | 182 | Montgomery | 39 14 25 N | 077 14 53 W |
| Owen Brown | Populated Place | 110 | Howard | 39 11 22 N | 076 50 32 W |
| Owen Brown Interfaith Center | Church | 104 | Howard | 39 11 14 N | 076 50 41 W |
| Owen Brown Middle School | School | 110 | Howard | 39 11 26 N | 076 50 37 W |
| Owen Brown Village Shopping Center | Locale | 105 | Howard | 39 11 10 N | 076 50 33 W |
| Owen Soper Woods | Populated Place | 44 | Calvert | 38 37 54 N | 076 32 34 W |
| Owens Branch | Stream | | Wicomico | 38 22 10 N | 075 36 56 W |
| Owens Creek | Stream | | Frederick | 39 34 44 N | 077 19 56 W |
| Owens Creek | Stream | | Wicomico | 38 30 16 N | 075 45 52 W |
| Owens Creek Camp | Locale | 402 | Frederick | 39 39 35 N | 077 29 14 W |
| Owens Park | Park | 156 | Montgomery | 39 10 58 N | 077 24 28 W |
| Owens Road Elementary School | School | 54 | Prince George's | 38 49 04 N | 076 58 49 W |
| Owens Road Park | Park | 73 | Prince George's | 38 49 06 N | 076 58 28 W |
| Owensville | Populated Place | 34 | Calvert | 38 44 11 N | 076 38 40 W |
| Owensville Church | Church | 55 | Anne Arundel | 38 51 03 N | 076 35 47 W |
| Owensville Church (historical) | Church | 37 | Anne Arundel | 38 50 52 N | 076 35 57 W |
| Owings | Populated Place | 27 | Calvert | 38 43 03 N | 076 36 05 W |
| Owings Beach | Populated Place | 2 | Anne Arundel | 38 46 21 N | 076 33 16 W |
| Owings Cliffs | Cliff | 21 | Anne Arundel | 38 44 49 N | 076 33 44 W |
| Owings Farm | Populated Place | 30 | Calvert | 38 42 33 N | 076 32 57 W |
| Owings Farm Pond Dam | Dam | 11 | Queen Anne's | 39 10 54 N | 076 00 17 W |
| Owings Hills | Populated Place | 29 | Calvert | 38 42 52 N | 076 36 15 W |
| Owings Mills | Populated Place | 152 | Baltimore | 39 25 10 N | 076 46 49 W |
| Owings Mills Commerce Center | Locale | 198 | Baltimore | 39 26 32 N | 076 46 27 W |
| Owings Mills Corporate Center | Locale | 160 | Baltimore | 39 24 06 N | 076 46 44 W |
| Owings Mills High School | School | 188 | Baltimore | 39 25 22 N | 076 47 35 W |
| Owings Mills Industrial Park | Locale | 140 | Baltimore | 39 24 44 N | 076 46 39 W |
| Owings Mills Library | Building | 158 | Baltimore | 39 25 01 N | 076 46 35 W |
| Owings Mills Post Office | Post Office | 139 | Baltimore | 39 24 44 N | 076 46 44 W |
| Owings Mills School | School | 172 | Baltimore | 39 25 36 N | 076 47 24 W |
| Owings Mills Town Center Shopping Center | Locale | 176 | Baltimore | 39 24 36 N | 076 47 24 W |
| Owings Mills Volunteer Fire Company Station 31 | Building | | Baltimore | 39 25 10 N | 076 46 45 W |
| Owings Post Office | Post Office | 27 | Calvert | 38 42 57 N | 076 35 59 W |
| Owings Ridge | Populated Place | 183 | Baltimore | 39 26 26 N | 076 47 28 W |
| Owings Station | Populated Place | 39 | Calvert | 38 42 42 N | 076 36 32 W |
| Owings Town Center | Populated Place | 17 | Calvert | 38 43 01 N | 076 36 17 W |
| Owings Trailer Park | Locale | 139 | Harford | 39 38 03 N | 076 16 24 W |
| Owings Wood | Populated Place | 7 | Calvert | 38 42 33 N | 076 32 24 W |
| Owl Branch | Stream | | Baltimore | 39 38 46 N | 076 39 40 W |
| Owl Hollow Acres | Populated Place | 10 | Worcester | 38 04 54 N | 075 26 15 W |
| Owl Point | Cape | 0 | Wicomico | 38 21 26 N | 075 37 04 W |
| Oxford | Populated Place | 2 | Talbot | 38 41 11 N | 076 10 18 W |
| Oxford Cemetery | Cemetery | 0 | Talbot | 38 41 21 N | 076 09 35 W |
| Oxford City Hall | Building | 2 | Talbot | 38 41 21 N | 076 10 22 W |
| Oxford Fire Company Station 20 | Building | | Talbot | 39 08 46 N | 076 17 18 W |
| Oxford Green | Populated Place | 50 | Prince George's | 39 03 43 N | 076 50 28 W |
| Oxford High School (historical) | School | 0 | Talbot | 38 41 01 N | 076 10 03 W |
| Oxford Museum | Building | 2 | Talbot | 38 41 20 N | 076 10 22 W |
| Oxford Neck | Cape | 2 | Talbot | 38 40 55 N | 076 08 21 W |
| Oxford Park | Park | 0 | Talbot | 38 41 02 N | 076 10 03 W |
| Oxford Police Department | Building | | Talbot | 39 08 02 N | 076 17 34 W |
| Oxford Post Office | Post Office | 2 | Talbot | 38 41 17 N | 076 10 22 W |
| Oxford United Methodist Church | Church | 2 | Talbot | 38 41 21 N | 076 10 25 W |
| Oxon Creek | Stream | | Prince George's | 38 48 26 N | 077 01 36 W |
| Oxon Hill | Populated Place | 57 | Prince George's | 38 48 12 N | 076 59 23 W |
| Oxon Hill Baptist Church | Church | 73 | Prince George's | 38 47 54 N | 076 58 59 W |
| Oxon Hill Branch Library | Building | 75 | Prince George's | 38 48 14 N | 076 58 58 W |
| Oxon Hill Branch Prince George's County Memorial Library | Building | 73 | Prince George's | 38 48 12 N | 076 59 01 W |
| Oxon Hill Cemetery | Cemetery | 58 | Prince George's | 38 48 08 N | 076 59 27 W |
| Oxon Hill Church of Christ | Church | 74 | Prince George's | 38 47 59 N | 076 56 08 W |
| Oxon Hill Elementary School | School | 52 | Prince George's | 38 47 03 N | 076 59 32 W |
| Oxon Hill High School | School | 56 | Prince George's | 38 47 52 N | 076 59 37 W |
| Oxon Hill Lutheran Church | Church | 41 | Prince George's | 38 48 09 N | 076 56 59 W |
| Oxon Hill Middle School | School | 23 | Prince George's | 38 45 42 N | 077 00 51 W |
| Oxon Hill Middle School | School | 39 | Prince George's | 38 47 00 N | 076 59 47 W |
| Oxon Hill Plaza Shopping Center | Locale | 56 | Prince George's | 38 48 16 N | 076 59 32 W |
| Oxon Hill Post Office | Post Office | 57 | Prince George's | 38 48 10 N | 076 59 25 W |
| Oxon Hill School (historical) | School | 73 | Prince George's | 38 47 54 N | 076 58 58 W |
| Oxon Hill United Methodist Church | Church | 60 | Prince George's | 38 48 04 N | 076 59 10 W |
| Oxon Hill Volunteer Fire Department Company 21 | Building | | Prince George's | 39 18 54 N | 077 39 04 W |
| Oxon Hill Volunteer Fire Department Company 42 | Building | | Prince George's | 39 22 21 N | 077 39 36 W |
| Oxon Run Hills | Populated Place | 56 | Prince George's | 38 50 38 N | 076 57 42 W |
| Oxys Hollow | Valley | | Frederick | 39 31 12 N | 077 27 20 W |
| Oyer Memorial Library | Building | | Prince George's | 38 58 38 N | 076 51 46 W |
| Oyster Cove | Bay | -14 | Dorchester | 38 29 30 N | 076 19 50 W |
| Oyster Cove | Bay | 2 | Kent | 39 07 44 N | 076 06 03 W |
| Oyster Cove | Bay | -7 | Somerset | 38 05 07 N | 076 03 07 W |
| Oyster Creek | Bay | -9 | Anne Arundel | 38 55 39 N | 076 28 02 W |
| Oyster Harbor | Populated Place | 4 | Anne Arundel | 38 55 28 N | 076 27 55 W |
| Oyster Point | Cape | 0 | St. Mary's | 38 03 27 N | 076 19 52 W |
| Oyster Pond | Lake | -3 | Worcester | 38 26 26 N | 075 05 49 W |
| Oystershell Creek | Stream | | Dorchester | 38 19 22 N | 075 55 20 W |
| Oystershell Point | Cape | 4 | Dorchester | 38 35 04 N | 075 59 58 W |
| Oystershell Point | Cape | 0 | Somerset | 37 55 50 N | 075 49 59 W |
| P B Dye Golf Club | Locale | | Frederick | 39 17 23 N | 077 20 19 W |
| P D Brown Memorial Branch Charles County Library | Building | 61 | Charles | 38 36 06 N | 076 53 59 W |
| Paca School | School | 11 | Baltimore (city) | 39 17 41 N | 076 34 45 W |