Blanche I (Basque: Zuria I.a) was Queen of Navarre from 1425 to 1441. She became queen regnant upon the death of her father King Charles III of Navarre. She served as Regent of Sicily in 1404–05 and in 1408–15.
Blanche was the second eldest daughter of King Charles III of Navarre and infanta Eleanor of Castile. She became heir to the throne of Navarre on the death of her elder sister, Joan, in 1413. Blanche married firstly Martin the Younger, King of Sicily and Prince of Aragon. They were married by proxy on 21 May 1402 in Catania. Blanche traveled to meet Martin, and they were married in person on 26 December 1402. The bride was about fifteen years old and the groom twenty-eight.
Blanche returned to Navarre where she was sworn in as heir to the throne in Olito the 28 October 1415, and was given allegiance by the lords. On 6 November 1419, Blanche married her second husband, John, duke of Peñafiel, the second son of Ferdinand I of Aragon and Eleanor of Alburquerque, by proxy in Olite. Charles III died on 8 September 1425 and Blanche succeeded him as Queen regnant of Navarre. John became King of Navarre in her right as John II, and the couple were crowned together in Pamplona 15 May 1429.
Blanche died in Santa María la Real de Nieva in 1441. After her death, John kept the government of Navarre in his own hands, from the hands of their own son Charles of Viana, the rightful heir of the line of Navarrese kings. He would become King of Aragon and King of Sicily upon the death of his elder brother Alfonso V of Aragon in 1458.