Henry I of Castile (14 April 1204 – 6 June 1217) was king of Castile. He was the son of Alfonso VIII of Castile and Eleanor of England, Queen of Castile (daughter of Henry II of England and Eleanor of Aquitaine).
In 1211 Henry became heir to the throne when his older brother Ferdinand suddenly died.
When his father died in 1214 Henry was just 10 years old so the regency was assumed by Henry's older sister Berengaria of Castile, wife of Alfonso IX of Leon.
In 1215 Henry married Mafalda of Portugal, daughter of Sancho I of Portugal. As he was very young, the marriage was not consummated, and it was dissolved in 1216 by Pope Innocent III on grounds of consanguinity. In the same year, Henry became betrothed to his second cousin Sancha, heiress of León.
Henry died in Palencia in 1217 at the age of 13, killed by a tile coming off a roof. His sister Berengaria succeeded him, before renouncing the throne in favour of her son Ferdinand III. His body was interred at Las Huelgas monastery in Burgos.