Francis III (Breton: Frañsez; French: François; 28 February 1518 – 10 August 1536) was Dauphin of France and, after 1524, Duke of Brittany.

The king had been badly defeated and captured at the Battle of Pavia (1525) and became a prisoner of Emperor Charles V, initially in the Alcázar in Madrid.

Francis almost immediately repudiated the treaty[3] and the eight-year-old Dauphin and his younger brother Henry spent the next three years as captives of Charles V, a period that scarred them for life.

[4] During his confinement in Spain, the Dauphin displayed a notably subdued demeanor compared to his more aggressive brother and seemed "to have accepted the rationale for his imprisonment reasonably well.

"[5] Nevertheless, the experience led him to become somewhat isolated, favoring black attire (like a Spaniard) and exhibiting a contemplative disposition seen as more Spanish than French.

[1] After playing a round of tennis at a jeu de paume court "pré[s] d'Ainay", the Dauphin asked for a cup of water, which was brought to him by his secretary, Count Montecuccoli.

Montecuccoli, who had been brought to the court by Catherine de' Medici, was accused of being in the pay of Charles V. When his quarters were searched, a book detailing several types of poison was discovered.