Charles Gonzaga (Italian: Carlo I Gonzaga) (6 May 1580 – 22 September 1637) was Duke of Mantua and Duke of Montferrat from 1627 until his death. He was also Duke of Rethel and Nevers, as well as Prince of Arches.

Born in Paris, he was the son of Louis Gonzaga, Duke of Nevers and Henriette of Cleves.

In 1600, as duke of Rethel, he founded, in Nevers, the Order of the Yellow Ribbon, soon forbidden by the King, due to its peculiar character.

In 1606, he decided the foundation of Charleville and the Principality of Arches ( )

In 1612, Charles, a descendant of the Byzantine Emperor Andronicus II Palaeologus through his grandmother Margaret, who was of the line of Theodore I, Marquess of Montferrat, Andronicus' son. Claimed the throne of Constantinople, at the time the capital of the Ottoman Empire. He began plotting with Greek rebels, including the Maniots of Greece, who addressed him as "King Constantine Palaeologus". When the Ottoman authorities heard about this, they sent an army of 20,000 men and 70 ships to invade Mani. They succeeded in ravaging Mani and imposing taxes on the Maniots. This caused Charles to move more actively for his crusade. He sent envoys to the courts of Europe looking for support. In 1619, he recruited six ships and some five thousand men, but he was forced to abort the mission because of the beginning of the Thirty Years' War.

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