Tweeddale (Scottish Gaelic: Srath Thuaidh/Tuaidhdail) is a committee area and lieutenancy area in the Scottish Borders Council district, southeastern Scotland. Its boundaries correspond to the historic county of Peeblesshire.
It is the traditional name for the dale (the area drained) by the upper reaches of the River Tweed. This area was considered to end before the Yarrow Water flowed into the Tweed, so the area was bounded to the south and east by the Yarrow/Tweed watershed, and to the north and east by the Gala Water/Tweed watershed.
12,770 ha of upper Tweedale between Broughton and Peebles is designated as the Upper Tweeddale National Scenic Area, one of 40 such areas in Scotland which are defined so as to identify areas of exceptional scenery and to ensure its protection from inappropriate development.
Tweeddale was also a historic district of Scotland, bordering Teviotdale and the Marches to the east, Liddesdale and Annandale to the south, Clydesdale to the west and Lothian to the north. It is within the historic former Peeblesshire.
The district which covered the Sheriffdoms of Peebles and Selkirk later became of the County of Peebles in the north and County of Selkirk or the "Ettrick Forest" in the south, two of the counties of Scotland.
The main reorganisation took place during the Local Government (Scotland) Act 1889, this Act established a uniform system of county councils and town councils in Scotland and officially restructured many of Scotland's counties.