Alte Weser, Maritime navigation tower at Weser River mouth, Germany.

Alte Weser is an offshore lighthouse standing in the water of the German Bight, off the mouth of the Weser. Its slender red shaft rises from a dark cylindrical base at the waterline and widens toward the top, where a white band, then a red band with small rectangular openings, encircle it. Above them a white railed platform carries a green lantern with a white roof and a thin mast. The tower is about 40 m high and built of steel-clad ferroconcrete.

The lighthouse was built in the early 1960s and replaced an earlier navigation tower that had guided ships since the late 1800s. Its completion marked the end of nearly a century of service by the older structure.

The tower's name refers to the Alte Weser fairway it guides; its lead light serves that channel, while separate orientation and cross-bearing lights mark the Neue Weser fairway. In fog it sounds the Morse letters "AL" once a minute. The tower appeared on a 20-pfennig Deutsche Bundespost stamp in the 1970s–80s, and in July 2024 the finance ministry issued a 70-cent stamp showing it.

The tower stands offshore in the German Bight, about 11 m below mean sea level at its base, and cannot be visited. It is seen with the naked eye from Wangerooge and the Wangerland coast, and in good weather from the viewing dune on Spiekeroog. At night its white light is visible toward the Weser estuary, even from Norderney on the horizon.

The tower's conical shaft, tapering downward, was designed by Bremerhaven engineer Andreas Carstens to reduce resistance to waves and drift ice. Its steel shaft and upper storeys were prefabricated in a dry dock at the Howaldtswerke in Kiel, towed through the Kiel Canal on a lift platform, and jetted into the sand. A first shaft was abandoned after a fatal leak in 1962; its stump remains in the seabed.