The Tumbling Weir is a circular weir in the town of Ottery St. Mary, Devon, England that allows water from a leat or man-made stream to reach the River Otter. It is apparently a rare design in that the water enters through a circular opening at the top that is surrounded by the stream. The water then cascades down some more smaller rings until it enters a culvert which enters a tunnel under the nearby path before sluicing down to the river a few metres away.