Kelso is a market town in the Scottish Borders area of Scotland. Within the boundaries of the historic county of Roxburghshire, it lies where the rivers Tweed and Teviot have their confluence. The town has a population of 5,639 according to the 2011 census and based on the 2010 definition of the locality. Kelso's main tourist attractions are the ruined Kelso Abbey and Floors Castle. The latter is a house designed by William Adam which was completed in 1726.