historic county in southeastern Scotland, occupying a rolling upland region dissected by the valleys of the Ettrick and Yarrow waters (rivers), which merge in the east with the River Tweed. Selkirkshire lies entirely within the Scottish Borders council area.

Archaeological evidence indicates that Selkirkshire was occupied by the Neolithic Period. Romans established military camps in the Ettrick valley and at Newstead. The history of the area for six centuries after the retreat of the Romans is that of southeastern Scotland as a whole. The county formed part of first the Celtic British kingdom of Strathclyde and then the Anglo-Saxon kingdom of Northumbria and finally, about 1020, it was annexed to Scotland. The region subsequently suffered centuries of border warfare between the Scots and the English to the south. By the 16th century the area was called Ettrick Forest and was a hunting ground for the Scottish kings. The novelist Sir Walter Scott (Scott, Sir Walter, 1st Baronet) was sheriff of Selkirkshire from 1799 until his death. Selkirkshire was largely bypassed by the Industrial Revolution and remains essentially rural in character, although woolen textile manufacture did develop in Galashiels and Selkirk town. Galashiels is the largest town in the county, and Selkirk was the historic county town (seat).