Longformacus is a parish, which lies in the Scottish Borders Council Area, some 8 miles (13 km) west of Duns in the Scottish Borders and 14 miles (22 km) southeast of Haddington in East Lothian.
It is located in the old county of Berwickshire, which disappeared following the Local Government (Scotland) Act 1974.
The parish has an area of 85.3 sq. km (32.9 sq. miles). Longformacus has 9 neighbouring parishes; namely Cranshaws, Duns, Garvald & Bara, Greenlaw, Langton, Lauder, Polwarth, Westruther and Whittingehame. The boundaries of this parish were modified among significant changes recommended by the Boundary Commissioners after the Local Government (Scotland) Act 1889.
