| River Calder | |
| Subdivision Type1: | Country |
| Subdivision Name1: | Scotland |
| Subdivision Type2: | Council area |
| Subdivision Name2: | Renfrewshire (mainly) |
| Subdivision Type5: | Towns/villages |
| Subdivision Name5: | Lochwinnoch |
| Mouth: | Castle Semple Loch |
| Mouth Coordinates: | 55.7929°N -4.6174°W |
The River Calder (Gaelic; Scottish Gaelic: Caladar) is a river mainly within Renfrewshire, Scotland.
The river rises in the hills to the west of the county and for some of its length forms the border between Renfrewshire and its neighbouring council areas of North Ayrshire and Inverclyde. The only significant settlement which the river runs through is Lochwinnoch, before flowing into the nearby Castle Semple Loch[1] [2] which drains into the Black Cart Water.