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 has a population of 17,394 at the latest census in 2001 it is the second smallest of the 5 committee areas in the Scottish Borders.
It is the traditional name for 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.
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.