Selkirkshire, also known as the County of Selkirk, was one of the 34 traditional counties into which Scotland was divided for administrative purposes. It occupied the middle reaches of the valley of the River Tweed and was home to much of the textile industry that once made the central part of the Scottish Borders so prosperous.
Selkirkshire was bordered on the west by Peeblesshire; on the north by Midlothian and Berwickshire; on the south east by Roxburghshire; and on the south by Dumfriesshire. It also had exclaves within the boundaries of two neighbours, Peeblesshire and Roxburghshire. These were given to the counties that surrounded them in a tidying up of the map of Scotland's counties which removed most enclaves and exclaves and reduced the total number of counties to 33 in 1890. Selkirkshire remained a county in its own right until reorganisation in 1975 swept all the counties away in favour of 12 regions.
The regions formed in 1975 were the upper tier of a two tier local authority system, and the area which had formed Selkirkshire became part of the region of Scottish Borders. Most regions were divided into a number of district council areas, and Scottish Borders had four of them. The area that had formed the traditional county of Selkirkshire became part of Ettrick & Lauderdale District, which also took over parts of what had been the traditional county areas of Berwickshire, Roxburghshire and Midlothian.
Regions disappeared from the scene in a major reorganisation in 1996, being replaced by 32 unitary council areas. What had started out as the traditional county of Selkirkshire today forms the geographic core of the unitary council area of Scottish Borders. For administrative purposes, Scottish Borders is divided into five area committee areas, which are partly based on the district council areas that preceded them. The Eildon area committee area inherited the boundaries of the Ettrick & Lauderdale District and so contains what was previously Selkirkshire.