Chatou lock, Lock and dam complex in Chatou, France

Chatou lock is a navigation and water control facility on the Seine River that regulates water levels for boat passage and manages river flow. The structure combines lock gates and dam components that work together to balance different water levels for vessels to pass through safely.

A first movable dam with double lifting gates was commissioned in July 1932 on a branch of the Seine and served until 2013. It was demolished between May and September 2014. The replacement, built from 2009 to 2013 a few metres downstream, was designed by architect Luc Weizmann and built by Bouygues Construction, with flap gates instead of lifting gates.

The current dam, built 2009–2013, was designed by architect Luc Weizmann and is listed in the general inventory of cultural heritage. Its flap gates replaced the double lifting gates of the 1932 structure, and a fish ladder lets migratory fish pass the Seine at Chatou. The red-and-white sign on the deck railing marks the crossing point.

The structure sits directly on the Seine and can be observed from the surrounding riverbank areas when boats pass through the lock. The best view of its operation comes from the banks or walkways near the facility.

The 2013 structure is not a lifting-gate dam: it uses flap gates and stands half as tall as the 1932 dam it replaced a few metres downstream. It also has a fish pass, so species can move upstream past the barrier. Architect Luc Weizmann designed it; Bouygues Construction built it for Voies navigables de France.