| Name | Location | County | Country | Power source | Type | Function | River |
| Dressing mills, Maenofferen Slate Mine, Blaenau Ffestiniog | Blaenau Ffestiniog, Ffestiniog | Merionethshire | United Kingdom | Electricity, Water | Watermill | Saw mill | Bowydd |
| Graig Ddu Slate Works, Blaenau Ffestiniog | Blaenau Ffestiniog, Ffestiniog | Merionethshire | United Kingdom | Water | Watermill | Quarry mill/wheel, Slate mill | |
| Slate mill, Drum Slate Quarry, Blaenau Ffestiniog | Blaenau Ffestiniog, Ffestiniog | Merionethshire | United Kingdom | Water | Watermill | Quarry mill/wheel, Slate mill | Gamallt |