A long narrow loch and former reservoir on the island of Bute in Argyll and Bute, Loch Fad extends southwestwards for nearly 1½ miles (2.5 km) along the line of the Highland Boundary Fault to the south of Rothesay. Kirk Dam extends the loch for a further mile (1.5 km) at its northeastern end. Engineer Robert Thom (1774 - 1847) diverted water into Loch Fad to power Rothesay's cotton mills, which were on the brink of bankruptcy due to the cost of importing coal. Today, Loch Fad provides excellent fishing, being well stocked with rainbow and brown trout.
The restored Bluebird K7 hydroplane was tested on the loch in 2018, 51 years after it crashed on Coniston Water in the English Lake District killing pilot Donald Campbell (1921-67), during an attempt on a world speed record.