Fort Saint-Jean (French pronunciation: [fɔʁ sɛ̃ʒɑ̃]) is a fortification in Marseille, built in 1660 by Louis XIV at the entrance to the Old Port.

Fort Saint-Jean was built on a site earlier occupied by the Military Order of the Knights Hospitaller of Saint John, from which the new building derived its name.

"[1] In fact, the two new forts were built in response to a local uprising against the governor, rather than for the defence of the city: their cannons pointed inwards towards the town, not outwards towards the sea.

[2] In April 1790, Fort Saint-Jean was seized by a revolutionary mob who decapitated the chevalier de Beausse, commander of the royal garrison, when he was captured after refusing to surrender the fortress.

Although returned to the French Army, Fort Saint-Jean remained in a neglected and disused state until it was passed to the Ministry of Cultural Affairs in 1960.