France once had a king who reigned for four days — his entire life

John I of France, called the Posthumous, was born on November 15, 1316, and died on November 19, 1316. He's the youngest person ever to be king of France, the only one to be king from birth, and the only one to hold the title for his entire life. His father, Louis X, had died months earlier, so the kingdom waited on the pregnancy of the widowed queen, Clementia of Hungary — a boy would be king the moment he was born. He was, for four days.

Infant mortality was high in medieval Europe, but rumors of poisoning spread immediately — one had him murdered with a pin by his aunt — because his uncle Philip took the throne, and John's father had also died in strange circumstances. The cause of death is still unknown.

Decades later, a rumor spread that the little king had never died — and a man named Giannino Baglioni stepped forward claiming to be John and heir to the throne. Louis I of Hungary allegedly recognized him; Pope Innocent VI refused to receive him. Baglioni was captured in Provence and died in prison in 1363, still insisting he was the king of France.

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