Hennebont is famed for its resistance, under Joanna of Flanders, the widow of Jean de Montfort, to the armies of Philip of Valois and Charles of Blois when besieged in 1342 during the War of the Breton Succession.

She personally led an attack on the enemy camp, setting fire to it and earned the nickname "Jeanne la Flamme" ("Joan the Fiery").

In August 1944, during the Allied invasion of Brittany, a large section of the old walled town, especially the ramparts, towers and medieval buildings, sustained major damage during the bombing of German positions entrenched in the downtown area.

The Garde du Vœu Hennebont table tennis team won the French championship title in 2005, 2006, 2007 and 2009 and is regularly qualified to play in the Champions League or ETTU.

The flagship team plays in Kerlano but will move to Inzinzac-Lochrist, within a new sports complex on the site of Mané-Braz, in order to be able to accommodate more spectators, in 2024.