Bertrand du Guesclin (c. 1320 – July 13, 1380), nicknamed "The Eagle of Brittany" or "The Black Dog of Brocéliande", is a Breton knight and French military commander during the Hundred Years' War.

He is Constable of France from 1370 to his death.

Well known for his Fabian strategy, he takes part in six pitched battles and wins the four in which he holds command.