Monsieur d'Orléans (16 April 1607 – 17 November 1611) was the second son and fourth child of Henry IV of France and his consort, Marie de' Medici.

Of frail health, he died of seizures brought on by hydrocephalus at the age of four, whereupon his title and betrothal were transferred to Gaston, his younger brother.

[1] Born at 22:00 on 16 April 1607, the day after Easter, the prince's birth was a source of tremendous joy for his father, King Henry.

[2] At his birth, Henry bestowed upon his son 10,000 Lt in land revenue, adding that he would be granted an annuity provided that he should serve his brother, the Dauphin, well.

As it had become customary for the second son of the king to receive the title of Duke of Orléans, news of the young prince's birth described him as "Monsieur d'Orléans".

[10][11] The playwright François Tristan l'Hermite, who, as a youngster, lived at the court of Henry IV and was often called upon to read stories to the king's own children, described Monsieur d'Orléans as extremely handsome, intelligent, sharp-witted and prone to taking pity on those around him.

[14] In 1610, Henry IV was stabbed to death by a Catholic fanatic in Paris and the Dauphin succeeded as Louis XIII, with Queen Marie as regent.

[17] The following day, the body of Monsieur d'Orléans was subjected to an autopsy, which revealed that his brain was of a soft consistency, filled with water and pus.