Longformacus is a small village in Berwickshire. It is to be found in the Lammermuir Hills about 6 miles northwest of Duns. The Dye Water runs through the village, flowing east towards its confluence with the Whiteadder Water nearby.
The opera Lucia di Lammermoor, written by Gaetano Donizetti and based on Sir Walter Scott's The Bride of Lammermoor, is set in Longformacus.
The Southern Upland Way, a long distance route which crosses the eponymous hills from coast to coast, passes through the village. The Sir Walter Scott Way from Moffat (Dumfriesshire) to Cockburnspath (Berwickshire) passes through Longformacus.
| ("Wikimedia Commons" has material|
- RCAHMS record for Longformacus
- Gazetteer for Scotland: Longformacus
- Borders Family History Society: Longformacus