Leaderfoot Viaduct is a railway viaduct over the River Tweed in the Scottish Borders, Scotland, UK. It is situated 2.5 km east of Melrose at grid reference NT574347.
The viaduct was opened on November 16, 1863 to carry the Berwickshire Railway, which connected Reston (on the East Coast Main Line between Berwick-upon-Tweed and Edinburgh) with St Boswells (on the Edinburgh to Carlisle "Waverley Line"), via Duns and Greenlaw. The engineers of the railway were Charles Jopp and Wylie & Peddie.
The arches, each of 43 feet (13 m) span, are of brickwork, and the abutments, piers and walls are of rustic-faced red sandstone. Some later strengthening of the abutments and piers with old rails and buttresses on the southern valley side is very obvious. The railway was severed by flooding during August 1948, after which passenger trains never ran west of Duns. Freight trains continued to run across the viaduct as far as Greenlaw until July 19, 1965.
The viaduct is in good condition, having been renovated by Historic Scotland between 1992 and 1995. Good views of it can be obtained from Drygrange Bridge and the modern A68 road bridge immediately downriver. There has been talk of including the viaduct in the local footpath network but it is not normally open to the public, although access to the bridge is fairly easy for those who wish to go up.