Plötzensee lock, Navigation lock in Charlottenburg-Nord, Germany.

Plötzensee lock is a double-chamber lock at kilometre 7.45 of the Berlin-Spandau Ship Canal in Charlottenburg-Nord. Its two chambers, built for Plauer Maß ships, are 67.20 metres long and 10 metres wide, with a sill depth of 3 metres. The structure rests on wooden piles, and its chamber walls and heads are of concrete, partly faced with clinker brick.

The first Plötzensee lock, built between 1847 and 1859 on the Spandau Canal, had a 47.50 m chamber with double stem gates facing opposite directions to withstand flooding from the unregulated Lower Spree. After the Charlottenburg weir and locks were built in 1882–1885, these gates were removed. The current double-chamber lock, founded on wooden piles with concrete and partly clinker-brick walls, opened in 1912 for 600-tonne ships of the Plauer Maß; its wooden gates were replaced by steel gates around 1927.

The lock takes its name from the nearby Plötzensee lake, not from pike in the canal. It lies at kilometre 7.45 of the Berlin-Spandau Ship Canal, and its two chambers separate an eight-kilometre Havel reach from a four-kilometre Spree reach. The waterway and lock are operated by the Wasserstraßen- und Schifffahrtsamt Spree-Havel.

The lock lies at kilometre 7.45 of the Berlin-Spandau Ship Canal in Charlottenburg-Nord, spanned to the south by the Southern Seestraßen Bridge. The southern chamber is out of service (as of 2024), so all vessels pass through the northern chamber. The waterway authority responsible for operation and upkeep is the Wasserstraßen- und Schifffahrtsamt Spree-Havel.

The first lock on this site, built around 1859, had double mitre gates facing opposite directions so it could hold back water from either the Havel or the Spree during floods. That precaution became unnecessary after the Untere Spree was regulated and the Charlottenburg weir and lock were built in 1882–1885.