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.
Today the mill site and the adjoining factory is unoccupied, awaiting re-development. Near the site is the Tumbling Weir Hotel, a converted 17th century thatched house, now a popular hotel and restaurant.