Sluice Modřany, Navigation lock in Modřany district, Prague, Czech Republic.

Sluice Modřany is a water step on the Vltava at river kilometre 66.75 in the Modřany gorge, comprising an 87-metre weir with three 27-metre fields and steel flaps, a lock chamber on the right bank divided into 90-metre and 85-metre sections, a canoe slalom channel with a retarder sluice on the left bank, and a small hydroelectric plant.

The lock was built between 1979 and 1987 as part of efforts to improve river navigation on the Vltava. This project was a major undertaking that expanded water transport capabilities throughout the waterway system.

Passenger boats have called at Modřany since 1865; after 1880 the service also carried commuters, but once riverside roads and railways were built it kept only a recreational role. Today one pair of Prague Steamboat Company boats passes the lock on summer weekends, on the Prague–Slapy route.

The lock is accessible during regular daytime hours, with passage available by request outside standard times. Be prepared for wait times when multiple boats need to pass through simultaneously.

A 90-metre service tunnel runs beneath the river, its ceiling 115 centimetres thick, giving access to the weir's machinery. The weir itself is 87 metres long with three 27-metre fields between 3-metre piers, and its steel flap gate is 3.30 metres high.