Phare du Grand-Charpentier, Offshore lighthouse in the Loire estuary, Saint-Nazaire, France

The Phare du Grand-Charpentier is a lighthouse in Saint-Nazaire positioned at the Loire River estuary with a truncated cone-shaped tower made of smooth masonry. The structure culminates in a lantern that marks the river entrance and serves as a vital navigation reference point.

In 1808 the Nantes architect Mathurin Crucy drew a pyramidal lighthouse for the port project he presented to Napoleon, but it stayed a drawing. From 1826 an iron beacon marked the Charpentiers rocks; a masonry tower replaced it in 1850, was rebuilt after a storm in 1877 and destroyed again in 1887. The present tower was built in 1884-1887, lit from 1888, switched off during the Second World War and relit on 13 August 1945.

The name comes from the Charpentiers rocks, not from shipwrights; the lighthouse is one of several marking the Loire estuary channel, alongside the Banche, Pilier and Aiguillon lighthouses. It cannot be visited, but its grey tower and green lantern can be seen from the Pointe de Chémoulin semaphore.

The lighthouse cannot be visited. Access is difficult: only a small boat can reach a 56-metre jetty before low tide. The tower stands on the Charpentiers rocky plateau, 1.3 nautical miles off Pointe de Chémoulin.

The lighthouse received heritage status in 2011, an honor that underscores its importance to French maritime engineering history. This designation protects the structure while preserving its continuing role as a vital navigation aid.