Henry died in a joust against the captain of his Scottish Guard, Gabriel, the Count of Montgomery. The fateful run occurred at the end of a tournament day, after Montgomery had almost unhorsed the king. Henry instead on another tilt. Montgomery's lance struck the king's helmet and shattered, with a long splinter running through the king's visor through his eye and into or near his brain. The king initially survived injury, and was attended to by two of the most celebrated physicians in Europe, Ambroise Paré and Andreas Vesalius. The queen, Catherine de Medici, ordered four prisoners executed with wood driven into their brains so that the physicians would have the chance to study the king's wound in detail on the corpses. Despite this rather extraordinary measure, the king deteriorated steadily. Vesalius' personal account is consistent with the development of meningitis or encephalitis. After 11 days, the king died.

During these 11 days, Montgomery is supposed to have come to the king's side, and asked to have his head and right hand cut off in punishment. The king told him that he had jousted well and bravely and that the accident was not his fault.

Following Henry's death, Catherine essentially ruled through a series of three of her sons. Montgomery retired to his estate in Normandy. From there, his history gets a bit complicated. He converted to Protestantism and took part in the religious fighting in Bourges and Rouen that followed the St. Bartholomew's Day Massacre in 1572. He escaped to England and remained there for about a year, later returning to attempt to lead a Huguenot insurrection in Normandy. He was captured by royal forces and executed in 1574.

Sourced, in part, "The Death of Henry II of France" Journal of Neurosurgery 12/1992