Seeschleuse Leer, Sea lock in Leer, Germany.

Seeschleuse Leer is a lock in Leer that connects the North Sea with the city's harbor, allowing vessels to move safely between different water levels. The installation serves both commercial shipping and recreational boats traveling through the region's waterway network.

Construction of the lock began on 10 May 1900 as part of a 1.5 million Goldmark harbour redevelopment, and it opened on 19 April 1903, making the port tide-independent. Built on the model of the IJmuiden sea lock, it was the only electrically operated lock in Prussia at the time. It was enlarged in 1960 and again in 1976, and renovated in 2020/2021.

The lock's opening on 19 April 1903 made the whole harbour tide-independent; in November 1903, partly at the urging of mayor August Dieckmann, preparations began for the Leerer Heringsfischerei, founded in June 1905. The lock was modelled on the sea lock at IJmuiden and was the only electrically operated lock in Prussia when built.

The lock chamber measures 192 metres long and 26 metres wide, with a sill depth allowing ships of up to 5.50 metres draft. It links the Leeraner Hafen via the Leda and Ems to the North Sea, so pleasure craft and commercial vessels pass through the same chamber. Boaters should check the current water level and waiting position before entering.

When it opened on 19 April 1903, the lock was the only electrically operated lock in Prussia, built on the model of the sea lock at IJmuiden. Its chamber was then 130 m long with a sill depth of seven metres.