The Peterborough lift lock is a boat lift located on the Trent Canal in the city of Peterborough, Ontario, Canada and is Lock 21 on the Trent-Severn Waterway.
The dual lifts are the highest hydraulic boat lifts in the world, rising 19.8 m (65 ft). This was a considerable accomplishment when conventional locks usually only had a 2 m (7 ft) rise. However it is not the highest boat lift in the world - the lift at Strépy-Thieu in Belgium being greater in both capacity (1,350 tonnes) and height difference (73.15 m).
No external power is needed, the lift lock functions by gravity alone using a counterweight system. When one side reaches the top position it stops about 5 cm (2 inches) below the adjoining canal's water level. When the gates open water flows into the ship basin until the water level rebalances. The weight of the extra water is enough to power the hydraulic lift. As the top level lowers to the bottom position it pushes the other side up to the top position where the cycle starts over again.
In the 1980s, a visitor's centre was built beside the lock. It offers interactive simulations of going over the lift lock in a boat, and also historical exhibits detailing the construction of the lift lock.
Many local residents of Peterborough skate on the canal below the lift lock in the winter.
The Peterborough lift lock was named a Historic Mechanical Engineering Landmark by the American Society of Mechanical Engineers in 1987.