Phare Carnot de Boulogne-sur-Mer, Coastal lighthouse at Port of Boulogne-sur-Mer, France.

Phare Carnot de Boulogne-sur-Mer is a white cylindrical lighthouse located at the end of the Carnot jetty within the city's harbor. The tower stands roughly 22 meters tall with a green top and occupies a prominent position on the breakwater.

A lighthouse stood here from 39 AD, when Caligula had one of the world's earliest towers built on the cliff at today's Calvaire des Marins, not at this jetty. Charlemagne restored it in 811, the English enclosed it with a brick fort in 1544, and it collapsed on 24 July 1644 after cliff erosion and a quarry at its foundations. The present tower was built in 1968.

The lighthouse serves as a recognizable landmark for the fishing community and maritime workers who navigate the harbor daily. Its distinctive green top makes it a visual reference point that locals and visitors alike use to orient themselves along the waterfront.

The lighthouse is reached by walking the length of the Carnot jetty, which sits on old fortifications and is covered by the sea at high tide, so time the walk with the tide tables. The tower itself is not open for climbing. Strong winds make the exposed jetty unsafe, and the concrete and stone base is slippery when wet.

The ancient Turris Ardens stood not here but on the cliff at today's Calvaire des Marins, 60 m high on an octagonal plan with 13 levels of alternating stone and brick. Charlemagne restored it in 811, the English ringed it with a brick fort in 1544, and it collapsed on 24 July 1644 after a quarry undermined the cliff.