Ercole Antonio Mattioli (1640-1694) was a minister of duke Charles IV of Mantua who was later captured and imprisoned by Louis XIV of France. He has been associated with the Man in the Iron Mask.

Mattioli was born at Bologna December 1 1640. He worked as a minister of Duke of Mantua who, in his position as marques of Montferrat, owned a frontier fortress of Casale near the French border. Louis XIV wanted the fortress and was willing to purchase it clandestinely for 100.000 crowns.

Mattioli successfully negotiated the trade and in gratitude, Louis XIV rewarded him lavishly. However, when the French were about to occupy the castle, Mattioli revealed the secret deal to governments of Austria, Savoy, Spain and Venice, possibly for additional rewards. Louis XIV had to cancel the deal and withdraw.

1679 Louis XIV had his French envoy d'Estrades kidnap Mattioli and bring him to France. There Mattioli was imprisoned in the fortress of Pignerol where he was eventually put into solitary confinement. By 1680 he was described as nearly mad.

Ercole Antonio Mattioli died 1694, still incarcerated.