The Lyne Water is a tributary of the River Tweed which rises in the Pentland Hills of southern Scotland at Baddinsgill Reservoir. It runs through West Linton and Romannobridge, passes Flemington and Lyne Station and enters the Tweed west of Peebles. It floods regularly in winter and occasionally in summer. There is free fishing above Flemington Bridge, and below Flemington the river is part of the Peebles fishing authority.
The river should not be confused with the River Lyne in Cumbria, England, or the River Lyne in Greater Manchester.