Blackweir is a suburban area in Cardiff, Cardiff
- Built-Up Area: Cardiff
- Parish/Community: Cathays
- Unitary Authority: Cardiff
- Region: Wales
- Category: Populated Place
- Type: Suburban Area
- Latitude/Longitude: 51°29'32"N 3°11'17"W
- Eastings/Northings: 317600, 177725
- OS Grid: ST176777
- Mapcode Local: GBR KGG.2Y
- Mapcode Global: VH6F6.PRB8
Location and coordinates are for the approximate centre of Blackweir within this administrative area.
Geographic features and populated places may cross administrative borders.