Blanche of Castile was Queen of France by marriage to Louis VIII. She acted as regent twice during the reign of her son, Louis IX: during his minority from 1226 until 1234, and during his absence from 1248 until 1252.

Louis VIII, nicknamed The Lion, was King of France from 1223 to 1226. As prince, he invaded England on 21 May 1216 and was excommunicated by a papal legate on 29 May 1216. On 2 June 1216, Louis was proclaimed "King of England" by rebellious barons in London, though never crowned. He soon seized half the English kingdom but was eventually defeated by the English and after the Treaty of Lambeth, was paid 10,000 marks, pledged never to invade England again, and was absolved of his excommunication.