Nenthorn is a small parish, which lies in the Scottish Borders Council Area, some 4 miles (6 km) northwest of Kelso and 9 miles (14 km) east of Melrose in the Scottish Borders.
It is located in the old county of Berwickshire, which disappeared following the Local Government (Scotland) Act 1974.
The parish has an area of 14 sq. km (5.4 sq. miles). Nenthorn has 6 neighbouring parishes; namely Earlston, Ednam, Hume, Kelso, Smailholm and Stichill. The boundaries of this parish were modified among significant changes recommended by the Boundary Commissioners after the Local Government (Scotland) Act 1889.