Alphonso or Alfonso (24 November 1273 – 19 August 1284), also called Alphonsus and Alphonse and styled Earl of Chester, was an heir apparent to the English throne who never became king.

He was born in Bayonne, Gascony, a duchy claimed by his maternal uncle King Alphonso X of Castile until his parents' marriage in 1254.

Queen Eleanor even persuaded her brother to travel to Gascony and serve as godfather at the young prince's baptism.

The Alphonso Psalter, now in the British Library, was completed a decade later when his sister Elizabeth married Margaret's brother, John I, Count of Holland, making the pairing of arms again appropriate.

As heirs apparent to the throne, both Alphonso and Edward bore the arms of the kingdom, differenced by a label azure.