| Official Name: | Karby |
| Pushpin Map: | Sweden Stockholm#Sweden |
| Subdivision Type: | Country |
| Subdivision Name: | Sweden |
| Subdivision Type3: | Municipality |
| Subdivision Name3: | Vallentuna Municipality |
| Subdivision Type2: | County |
| Subdivision Name2: | Stockholm County |
| Subdivision Type1: | Province |
| Subdivision Name1: | Uppland |
| Area Footnotes: | [1] |
| Area Total Km2: | 0.46 |
| Population As Of: | 31 December 2020 |
| Population Footnotes: | [2] |
| Population Total: | 838 |
| Population Density Km2: | auto |
| Timezone: | CET |
| Utc Offset: | +1 |
| Timezone Dst: | CEST |
| Utc Offset Dst: | +2 |
| Coordinates: | 59.5667°N 31°W |
Karby is a locality situated in Vallentuna Municipality, Stockholm County, Sweden.